thesis about scientific revolution

Thomas Kuhn and the Structure of Scientific Revolutions

Thomas Samuel Kuhn (1922-1996), pic by Davi.trip, CC-BY-SA-4.0

On July 18 , 1922 , American physicist , historian , and philosopher of science Thomas Samuel Kuhn was born. He is most famous for his controversial 1962 book The Structure of Scientific Revolutions , which was influential in both academic and popular circles, introducing the term “ paradigm shift “, which has since become an English-language idiom .

“Only when they must choose between competing theories do scientists behave like philosophers.” — Thomas Kuhn, Logic of Discovery or Psychology of Research? (1970)

Thomas Kuhn – Early Years

Kuhn was born in Cincinnati, Ohio , to Samuel L. Kuhn, who was trained as a hydraulic engineer at Harvard University and the Massachusetts Institute of Technology ( MIT ), and his wife  Minette. He attended the Hessian Hills School in Croton-on-Hudson , New York , a liberal school that encouraged students to think independently, and graduated from The Taft School in Watertown, CT , in 1940 , where he became aware of his serious interest in mathematics and physics . He obtained his B.S. degree in physics from Harvard University in 1943 with summa cum laude . After graduation , he worked on radar for the Radio Research Laboratory at Harvard and later for the U.S . Office of Scientific Research and Development   in Europe . He returned to Harvard at the end of the war , obtained his master’s degree  in physics in 1946 , and worked toward a PhD degree in the same department , which he obtained in 1949 under the supervision of John Van Vleck . According to his autobiographical notes , his three years of total academic freedom as a Harvard Junior Fellow were crucial in allowing him to switch from physics to the history and philosophy of science .

“Out-of-date theories are not in principle unscientific because they have been discarded. That choice, however, makes it difficult to see scientific development as a process of accretion.” — Thomas Kuhn, The Structure of Scientific Revolutions (1962)

Seeing through the Eyes of the Author

“Scientific revolutions are inaugurated by a growing sense… that an existing paradigm has ceased to function adequately in the exploration of an aspect of nature to which that paradigm itself had previously led the way.” — Thomas Kuhn, The Structure of Scientific Revolutions (1962)

The History of Science

The structure of scientific revolutions, paradigm shift.

The enormous impact of Kuhn’s work can be measured in the changes it brought about in the vocabulary of the philosophy of science : besides “ paradigm shift “, Kuhn popularized the word “ paradigm ” itself from a term used in certain forms of linguistics and the work of Georg Lichtenberg to its current broader meaning,[ 5 ] coined the term “normal science” to refer to the relatively routine, day-to-day work of scientists working within a paradigm, and was largely responsible for the use of the term “scientific revolutions” in the plural, taking place at widely different periods of time and in different disciplines, as opposed to a single “ Scientific Revolution ” in the late Renaissance . The frequent use of the phrase “ paradigm shift ” has made scientists more aware of and in many cases more receptive to paradigm changes, so that Kuhn’s analysis of the evolution of scientific views has by itself influenced that evolution.

The Process of Scientific Change

Kuhn explains the process of scientific change as the result of various phases of paradigm change.

• Phase 1: It exists only once and is the pre-paradigm phase , in which there is no consensus on any particular theory. This phase is characterized by several incompatible and incomplete theories. Consequently, most scientific inquiry takes the form of lengthy books, as there is no common body of facts that may be taken for granted.
• Phase 2: Normal science begins, in which puzzles are solved within the context of the dominant paradigm. As long as there is consensus within the discipline, normal science continues. Over time, progress in normal science may reveal anomalies, facts that are difficult to explain within the context of the existing paradigm.
• Phase 3 : If the paradigm proves chronically unable to account for anomalies, the community enters a crisis period . Crises are often resolved within the context of normal science. However, after significant efforts of normal science within a paradigm fail, science may enter the next phase.
• Phase 4 : Paradigm shift , or scientific revolution, is the phase in which the underlying assumptions of the field are reexamined and a new paradigm is established.
• Phase 5 : Post-Revolution , the new paradigm’s dominance is established and so scientists return to normal science, solving puzzles within the new paradigm.

The Structure of Scientific Revolutions is one of the most cited academic books of all time. Kuhn’s contribution to the philosophy of science marked not only a break with several key positivist doctrines, but also inaugurated a new style of philosophy of science that brought it closer to the history of science. Years after the publication of The Structure of Scientific Revolutions, Kuhn dropped the concept of a paradigm and began to focus on the semantic aspects of scientific theories. In particular, Kuhn focuses on the taxonomic structure of scientific kind terms. As a consequence, a scientific revolution is not defined as a ‘change of paradigm’ anymore, but rather as a change in the taxonomic structure of the theoretical language of science

References and Further Reading:

• [1] Thomas S. Kuhn at Britannica Online
• [2]” Kuhn, Thomas Samuel. ” Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com
• [3]  Bird, Alexander.   “Thomas Kuhn” . In   Zalta, Edward N.   (ed.).   Stanford Encyclopedia of Philosophy .
• [4]  Niels Bohr and the beginnings of Quantum Mechanics , SciHi Blog
• [5] Georg Christoph Lichtenberg – Master of Aphorism , SciHi Blog
• [6]  Notes for Thomas Kuhn’s “The Structure of Scientific Revolutions”
• [7] James A. Marcum, “ Thomas S. Kuhn (1922–1996) “,   Internet Encyclopedia of Philosophy
• [8]  Thomas S. Kuhn   (obituary,   The Tech   p. 9 vol 116 no 28, June 26, 1996)
• [9]  Kuhn, T. S.  The Structure of Scientific Revolutions . Chicago: University of Chicago Press, 1962. 
• [10]  Kuhn, T. S.  The Copernican Revolution: Planetary Astronomy in the Development of Western Thought . Cambridge: Harvard University Press, 1957.
• [11] Thomas S. Kuhn at Wikidata
• [12]  Philosophy of Science: Kuhn, Structure of Scientific Revolutions, lecture 1 ,  Abraham Stone  @ youtube
• [13] Timeline for Thomas Kuhn, via Wikidata

Harald Sack

Related posts, sidney fox and his research for the origins of life, frederick william twort and the bacteriophages, john herschel – a pioneer in celestial photography, georg cantor and the beauty of infinity.

Pingback: Toward the Next Paradigm in Economics?

There are large parts of the scaffolding introduced by Kuhn that is to the point and useful. However, much of the historical basis is flawed, essentially based on myths. For example, the idea that a astronomy was in a crisis when the Copernican revolution happened, there is no basis for that assertion. I highly recommend the writing of Owen Gingerich, especially https://dash.harvard.edu/handle/1/4258973

Thank you. The communication of science is critical in our day. Dr. Kuhn’s navigation through “this” and “not that” while avoiding “that” and “not this” can be a little thick. Valuable. Also see S. Chandrasekhar’s Truth and Beauty. (I have yet to find resonance with R. Dawkins Books too give a life. +/-)

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• Published: 11 April 2012

In retrospect: The Structure of Scientific Revolutions

• David Kaiser 1  

Nature volume  484 ,  pages 164–165 ( 2012 ) Cite this article

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David Kaiser marks the 50th anniversary of an exemplary account of the cycles of scientific progress.

The Structure of Scientific Revolutions: 50th Anniversary Edition

• Thomas S. Kuhn

Fifty years ago, a short book appeared under the intriguing title The Structure of Scientific Revolutions . Its author, Thomas Kuhn (1922–1996), had begun his academic life as a physicist but had migrated to the history and philosophy of science. His main argument in the book — his second work, following a study of the Copernican revolution in astronomy — was that scientific activity unfolds according to a repeating pattern, which we can discern by studying its history.

Kuhn was not at all confident about how Structure would be received. He had been denied tenure at Harvard University in Cambridge, Massachusetts, a few years before, and he wrote to several correspondents after the book was published that he felt he had stuck his neck “very far out”. Within months, however, some people were proclaiming a new era in the understanding of science. One biologist joked that all commentary could now be dated with precision: his own efforts had appeared “in the year 2 B.K.”, before Kuhn. A decade later, Kuhn was so inundated with correspondence about the book that he despaired of ever again getting any work done.

By the mid-1980s, Structure had achieved blockbuster status. Nearly a million copies had been sold and more than a dozen foreign-language editions published. The book became the most-cited academic work in all of the humanities and social sciences between 1976 and 83 — cited more often than classic works by Sigmund Freud, Ludwig Wittgenstein, Noam Chomsky, Michel Foucault or Jacques Derrida. The book was required reading for undergraduates in classes across the curriculum, from history and philosophy to sociology, economics, political science and the natural sciences. Before long, Kuhn's phrase “paradigm shift” was showing up everywhere from business manuals to cartoons in The New Yorker .

Kuhn began thinking about his project 15 years before it was published, while he was working on his doctorate in theoretical physics at Harvard. He became interested in developmental psychology, avidly reading works by Swiss psychologist Jean Piaget about the stages of cognitive development in children.

Kuhn saw similar developmental stages in entire sciences. First, he said, a field of study matures by forming a paradigm — a set of guiding concepts, theories and methods on which most members of the relevant community agree. There follows a period of “normal science”, during which researchers further articulate what the paradigm might imply for specific situations.

In the course of that work, anomalies necessarily arise — findings that differ from expectations. Kuhn had in mind episodes such as the accidental discoveries of X-rays in the late nineteenth century and nuclear fission in the early twentieth. Often, Kuhn argued, the anomalies are brushed aside or left as problems for future research. But once enough anomalies have accumulated, and all efforts to assimilate them to the paradigm have met with frustration, the field enters a state of crisis. Resolution comes only with a revolution, and the inauguration of a new paradigm that can address the anomalies. Then the whole process repeats with a new phase of normal science. Kuhn was especially struck by the cyclic nature of the process, which ran counter to then-conventional ideas about scientific progress.

At the heart of Kuhn's account stood the tricky notion of the paradigm. British philosopher Margaret Masterman famously isolated 21 distinct ways in which Kuhn used the slippery term throughout his slim volume. Even Kuhn himself came to realize that he had saddled the word with too much baggage: in later essays, he separated his intended meanings into two clusters. One sense referred to a scientific community's reigning theories and methods. The second meaning, which Kuhn argued was both more original and more important, referred to exemplars or model problems, the worked examples on which students and young scientists cut their teeth. As Kuhn appreciated from his own physics training, scientists learned by immersive apprenticeship; they had to hone what Hungarian chemist and philosopher of science Michael Polanyi had called “tacit knowledge” by working through large collections of exemplars rather than by memorizing explicit rules or theorems. More than most scholars of his era, Kuhn taught historians and philosophers to view science as practice rather than syllogism.

Most controversial was Kuhn's claim that scientists have no way to compare concepts on either side of a scientific revolution. For example, the idea of 'mass' in the Newtonian paradigm is not the same as in the Einsteinian one, Kuhn argued; each concept draws meaning from separate webs of ideas, practices and results. If scientific concepts are bound up in specific ways of viewing the world, like a person who sees only one aspect of a Gestalt psychologist's duck–rabbit figure, then how is it possible to compare one concept to another? To Kuhn, the concepts were incommensurable: no common measure could be found with which to relate them, because scientists, he argued, always interrogate nature through a given paradigm.

Perhaps the most radical thrust of Kuhn's analysis, then, was that science might not be progressing toward a truer representation of the world, but might simply be moving away from previous representations. Knowledge need not be cumulative: when paradigms change, whole sets of questions and answers get dropped as irrelevant, rather than incorporated into the new era of normal science. In the closing pages of his original edition, Kuhn adopted the metaphor of Darwinian natural selection: scientific knowledge surely changes over time, but does not necessarily march towards an ultimate goal.

Scientists have no way to compare concepts on either side of a scientific revolution.

And so, 50 years later, we are left with our own anomaly. How did an academic book on the history and philosophy of science become a cultural icon? Structure was composed as an extended essay rather than a formal monograph: it was written as an entry on the history of science for the soon-to-be-defunct International Encyclopedia of Unified Science . Kuhn never intended it to be definitive. He often described the book (even in its original preface) as a first pass at material that he intended to address in more detail later.

To me, the book has the feel of a physicist's toy model: an intentionally stripped-down and simplified schematic — an exemplar — intended to capture important phenomena. The thought-provoking thesis is argued with earnestness and clarity, not weighed down with jargon or lumbering footnotes. The more controversial claims are often advanced in a suggestive rather than declarative mode. Perhaps most important, the book is short: it can be read comfortably in a single sitting.

For the 50th-anniversary edition, the University of Chicago Press has included an introductory essay by renowned Canadian philosopher Ian Hacking. Like Kuhn, Hacking has a gift for clear exposition. His introduction provides a helpful guide to some of the thornier philosophical issues, and gives hints as to how historians and philosophers of science have parted with Kuhn.

The field of science studies has changed markedly since 1962. Few philosophers still subscribe to radical incommensurability; many historians focus on sociological or cultural features that received no play in Kuhn's work; and topics in the life sciences now dominate, whereas Kuhn focused closely on physics. Nevertheless, we may still admire Kuhn's dexterity in broaching challenging ideas with a fascinating mix of examples from psychology, history, philosophy and beyond. We need hardly agree with each of Kuhn's propositions to enjoy — and benefit from — this classic book.

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David Kaiser is Germeshausen Professor of the History of Science at the Massachusetts Institute of Technology in Cambridge. His latest book is How the Hippies Saved Physics (Norton, 2011).,

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Kaiser, D. In retrospect: The Structure of Scientific Revolutions. Nature 484 , 164–165 (2012). https://doi.org/10.1038/484164a

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5 The Scientific Revolution

• Published: January 2023
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This chapter surveys the transformations in scientific understanding that took place during the period usually known as the Scientific Revolution, roughly from 1500 to 1700, It follows the growing emphasis on experiment in science and charts the shift from an Aristotelian and Ptolemaic geocentric view of the universe to a Copernican heliocentric one. It looks at the development of new ideas about the generation of life, anatomy, and physiology. It also looks at the important changes in the culture of knowledge that took place during this period, with the emergence of new kinds of scientific institutions such as the Royal Society in England, and the Royal Academy of Science in France.

Although still contested by historians who prefer to emphasize the continuities underlying all historical change, the ‘Scientific Revolution’ has become the accepted designation for the period during which something recognizably like modern science emerged. While this term is arguably a misnomer—since the ‘revolution’ took about two centuries to accomplish—there can be no denying that the human endeavour to understand the natural world underwent such radical changes beginning in the sixteenth century that by the end of the seventeenth century there had been a complete sea-change. It was the fully comprehensive nature of these developments, and the truly remarkable achievements arising from them, which have led to the period being seen as one of revolution.

Between 1500 and 1700 the world picture shifted from a geocentric finite cosmos of nested heavenly spheres which allowed no empty space, to a heliocentric solar system in an infinite universe that was void except where it was dotted with stars. A prevailing belief in a qualitative dichotomy between the heavens and the Earth (the heavens being conceived as completely different from the Earth) gave way to the belief that planets were like the Earth, and stars like the Sun, and the acceptance of the universal applicability of the laws of nature. Moreover, the laws of nature were no longer simply conceived as mere regularities (bees make honey, the Sun rises in the East), but became codified for the first time as precise statements about how specific aspects of the world work, and were seen as capturing causal relationships between phenomena and as having predictive power. There arose new theories of motion, of the generation of life and its organization, a revised human anatomy, and a new physiology. This period also saw the introduction of the experimental method into what had previously been an essentially contemplative ‘natural philosophy’, and a new belief that mathematical analysis, in spite of its clearly abstract nature, could be used to help in understanding experimental results, and in understanding the physical world more generally. The previously contemplative natural philosophy also underwent dramatic change when it embraced the idea, previously confined to practitioners of mathematical and occult arts, that knowledge of the natural world should be put to use for the benefit of mankind. Going hand in hand with these changes was the emergence of new forms of organization and institutionalization among those with an interest in studying the natural world; in particular it was a period which saw the formation of societies devoted to the understanding of nature. The Scientific Revolution took place in Western Europe and, although in large part its starting point was the knowledge of the natural world first developed in ancient Greece and subsequently transformed by Islamic scholars and then by medieval Christian scholars, it went far beyond what these earlier civilizations and others such as the Chinese had achieved. Although science has now become an international enterprise, it is still fair to say that, for example, a Japanese Nobel Prize winner in Physics is a practitioner of Western science (in the same way that a Japanese concert pianist, or violinist, plays Western music). The story of the Scientific Revolution, therefore, is also, in part, the story of the rise of the West. Certainly, it is a story of the origins of how knowledge of the natural world, what we now call scientific knowledge, became so prominent in Western, and subsequently world, culture.

The literature on the Scientific Revolution is vast and wonderfully rich and complex. What’s more, it is still growing. What follows is a necessarily selective account of those aspects of the revolution which have acquired the highest profile in the historiography of science.

How It All Began: The Renaissance and the Scientific Revolution

It is easy to see that the Scientific Revolution, like the Protestant Reformation, constitutes an important part of the wider changes in intellectual authority that were characteristic of the period known to historians as the Renaissance, and so it can be said to share the same general causes as this major change in European history. A full account of its causes would, therefore, have to encompass the decline of the old feudal system and the rise of commerce, together with the concomitant rise of strong city-states and national monarchies during a period of increasing decline of the Roman Catholic Church and the Holy Roman Empire. In a brief account like this one, however, we must confine ourselves to those initiating causes which can be seen to have had the most direct effects. But before turning to these, it is also worth noting that the Renaissance itself should not be seen as having its own prior identity which enables us to see the Scientific Revolution as a mere spin-off of this larger movement—the changes that constituted the Scientific Revolution, no less than the changes that constituted the Protestant Reformation, were part and parcel of the changes which have led historians to see the Renaissance as a major turning point in history, and helped to make the Renaissance what it was.

Many of the changes in the Renaissance stemmed from the invention of printing, and the new exploitation of the magnetic compass and gunpowder (which were evidently known long before in the East), all of which had major cultural and economic repercussions. These can also be seen to have had a direct bearing upon developments in, and attitudes towards, natural knowledge. Printing, and the manufacture of paper (also adopted from the East), enabled the dissemination of knowledge as never before; and the compass and gunpowder demonstrated just how useful knowledge of the natural powers of things could be.

The magnetic compass made it possible for mariners to strike out across the open sea, instead of hugging coastlines, and played a significant role in the Renaissance voyages of discovery. But these voyages had another highly significant effect on subsequent thinking. It is not true that educated thinkers before the discovery of the New World by Christopher Columbus (1451–1506), assumed that the Earth was flat. The ancient Greeks knew that it was spherical, and the influential early Church Father, St Augustine (354–430), cautioned Christians against taking the Bible literally when it implied the world was flat, because they would only embarrass themselves in the eyes of pagans. Even so, throughout the Middle Ages the idea developed that the sphere of the Earth was floating in a larger sphere of water, with only one hemisphere of the Earth above the water. This idea developed out of starting assumptions taken from Aristotle (384–322 bc ), the ancient Greek thinker whose authority came to dominate medieval natural philosophy. There was, however, an alternative view, promoted by Claudius Ptolemy ( c .90– c .168), a later ancient Greek writer, who had become the major authority in the technical subjects of astronomy and astrology. Ptolemy’s Geography (or Cosmography , as it was translated) became newly available to the Latin West in 1406 and it was clear from this that he simply believed in a single ‘terraqueous globe’—that is to say, the Earth was simply a single sphere whose surface was made up of land masses and oceans or seas; there was no extra sphere of water, in which the Earth was floating. Ptolemy’s Geography on the one hand encouraged the great navigators of the Renaissance period to believe it might be possible to circumnavigate the globe (without becoming lost in the supposed larger sphere of water, in which the globe was held to be floating), while on the other hand the Renaissance circumnavigations of the globe showed that Ptolemy was correct, and the supposedly Aristotelian theories developed by medieval philosophers were wrong.

But there were a couple of other major effects of these voyages. Exploration of the New World and other parts beyond Europe gave rise to an increasing awareness of cultural relativism. This was especially remarkable in the case of China, where a highly advanced civilization had no connection whatsoever to the Judaeo-Christian religious tradition which had previously been regarded as synonymous with civilization. Furthermore, it showed that the traditional wisdom (again deriving from Aristotle’s authority, but in this case also supported by Ptolemy), that life could not survive in the antipodes, was misconceived.

This brings us to another major aspect of the Renaissance which was to have far-reaching repercussions on the understanding of the natural world. Some of the political and economic changes in the Renaissance manifested themselves in the emergence of powerful and wealthy individuals or families (exemplified most clearly, for example, by the ruling families in the different city states of Renaissance Italy—the Medici in Florence, the Sforza in Milan, and so on) who could demonstrate and enhance their standing by acting as secular patrons to artists and scholars. It was these secular patrons who enabled the visual arts to flourish in this period—which is, of course, one of the most prominent features of the Renaissance. Equally important for our purposes, however, was the patronage of scholars, who were encouraged to gather libraries of great books for their patrons. The result was a re-discovery of the writings of many ancient philosophers, and the concomitant realization that Aristotle was not the philosopher, as medieval philosophers and theologians referred to him, but was merely a philosopher. Furthermore, the discovery of books about ancient philosophy, most notably The Lives of the Philosophers , by Diogenes Laertius ( fl . second century ad ), made it clear that, for the ancients themselves, Aristotle was by no means the most admired philosopher.

It is important to note here that the curriculum in the Arts Faculties of all the universities throughout Europe was largely based on the natural philosophy of Aristotle. Since all students had to become masters of arts before they could proceed to study in the so-called higher faculties (of theology, law, and medicine), this meant that the most highly educated people throughout Europe were thoroughly steeped in Aristotelian natural philosophy. Their investment was now looking increasingly ill-founded. The discovery of writings by other philosophers, including Plato ( c. 427–347 bc ), the Neoplatonists, Stoics, and Epicureans, provided a rich fund of alternatives. Eclectic attempts to combine the best features of the newly available ancient philosophies met with some success in moral and political philosophy, but were less successful in natural philosophy. One alternative, therefore, was to switch allegiance from Aristotle to Plato, or some other ancient thinker. Other Renaissance philosophers, however, perhaps more disorientated or more dismayed by the overthrow of traditional intellectual authority, tended increasingly to reject recourse to any authority and turned to personal experience as the best means of acquiring knowledge of nature. An important influence here was the fact that one of the revived ancient philosophies, which was seen to be popular among the ancients themselves, was scepticism—with its built-in rejection of authority.

The voyages of discovery, and the re-discovery by scholars of alternative philosophies to that of Aristotle, increasingly led to a rejection of human authority as a valid source of knowledge. This in turn had repercussions in religion, and these fed back into negative attitudes to authority. When Martin Luther (1483–1546) rejected the authority of the Pope and the priest in religion, urging instead that every man should be his own priest in the priesthood of all believers, he encouraged the faithful to read the Bible for themselves. In our secular world, we might regard this merely as an affirmation of the authority of the Bible. But for Luther, the human authority of the Pope, or the local priest, was coming between the believer and the source of truth. So, to read the Bible for oneself (something which was forbidden to the ordinary believer at the time) was to reject authority and to go to the source. The natural world was often regarded as God’s other book, and just as the faithful were now expected to read the Book of Scripture for themselves, so it seemed to devout natural philosophers that God could be served by reading the Book of Nature. Natural philosophy had come to be seen, in the Middle Ages, as the hand-maiden to the so-called ‘Queen of the Sciences’, theology. Before the Renaissance there was only one theology, represented by Roman Catholic orthodoxy, and only one natural philosophy, represented by the scholastic Aristotelianism developed by the medieval schoolmen. Apart from all the other effects of the fragmentation of Western Christianity after the Reformation, there was its effect on reinforcing the rejection of human authority and emphasizing the need to go to the source of truth. In the case of natural philosophy this simply meant the natural world itself. Where natural philosophers had once sought the answer to any question about the natural world in the books of Aristotle, this was now seen to be indefensible. The alternative was to study the natural world itself. Simple and obvious though this might seem to us, it represents a major and crucially important shift in the history of human endeavour.

The time was ripe for the development of a new experiential or empiricist approach to the understanding of the physical world. This new attitude was clearly exemplified by the radical Swiss religious, philosophical, and medical reformer known as Paracelsus (1493–1541). He not only wrote reformist works, developing a uniquely original system of medicine, but he also explicitly defended his new approach on empiricist grounds. In an announcement of the course he intended to teach at the University of Basle in 1527, for example, he rejected ‘that which those of old taught’ in favour of ‘our own observation of nature, confirmed by extensive practice and long experience’. It is easy to see, from the vigorous reaction against Paracelsus, that his rejection of the authority of Galen ( c .130–201) and Avicenna (980–1037), who played the same authoritative roles in medicine as Aristotle and St Thomas Aquinas (1225–74) did in natural philosophy, was seen by many not just as an attack on the traditional medicine sanctioned by the colleges of physicians throughout Europe, but as an attack on the colleges themselves, and even as an attack on the Church and State, of which the colleges were seen as representatives. Just two years after Charles I (1600–49) was beheaded outside the Palace of Whitehall, the Royal College of Physicians in London was denounced as a ‘Palace Royal of Galenical Physick’. When the sectarian herbalist Nicholas Culpeper (1616–54) translated the College-sponsored Pharmacopoeia into English for the first time (1649) he made an even more damaging comparison: ‘Papists and the College of Physicians will not suffer Divinity & Physick to be printed in our mother tongue.’

In spite of the radical and subversive nature of much of Paracelsus’ teaching, many aspects of his new system of medicine were embraced by and absorbed into revised versions of more traditional medicine. One of the reasons for this was undoubtedly the perceived empirical success of Paracelsianism, so lending support to the efficacy of this new methodology. Doctors, after all, were professionals seeking to make a living from fee-paying patients; if new therapies seemed to lead to new cures, it was inevitable that these would be sought out by patients, and provided by practitioners. But increased empiricism took hold even in areas of medicine which had no immediate bearing on therapeutic success. The reputation of Andreas Vesalius (1514–64) was not just based on his superbly illustrated anatomical textbook, De humani corporis fabrica ( On the Structure of the Human Body , 1543), a book which surely shows the crucial importance of printing, but also on his new method of teaching. Where previously anatomy lecturers read from one of Galen’s anatomical works, while a surgeon performed the relevant dissections, Vesalius dispensed with the readings and performed his own dissections, talking the students through the procedure and what it revealed. Shortly afterwards (1594), his university, at Padua, constructed the first purpose-built anatomical lecture theatre, with steeply raked tiers of seats, enabling all students a clear and not-too-distant view of the cadaver.

Paracelsus, and no doubt others even outside the ranks of his followers, failed to see any value to the physician in the ‘anatomy of corpses’, but eventually the heightened level of anatomical study was to have practical benefits. A number of new discoveries by Vesalius and his successors at Padua, as well as their emphasis upon the importance of comparative anatomy for the understanding of the human body, was to lead to William Harvey’s discovery of the circulation of the blood.

Harvey (1578–1657) was a student at Padua between 1597 and 1602, and continued with the kind of anatomical study he learned at Padua upon his return to England. Where other medical schools focused only on the human body, the Paduan emphasis upon the value of comparative anatomy allowed Harvey to perform vivisections on dogs and other animals. This enabled Harvey to see beating hearts in action, and to go far beyond what was possible by simply inspecting dead human hearts. Harvey was able to show that the Galenic assumption of two separate systems in the body—the veinous system originating from the liver, and the arterial system originating from the heart—was completely wrong, and that there was only one system taking blood out from the heart to all parts of the body via the arteries, and bringing it back by the veins, to be re-circulated endlessly. Although resisted at first, Harvey’s experimental demonstrations of his discovery (published in 1628) were so elegant, and his audience so used by now to the relevance of experiment in revealing truths about nature, that his theory soon became accepted. This immediately meant that the whole system of Galenic physiology had to be recast. The result was a marshalling of effort by anatomists and physiologists throughout Europe, leading successively to numerous new discoveries.

Vesalius claimed that he had discovered over 200 errors in Galen’s anatomical works; he blamed these on the fact that Galen was forbidden by his Roman overlords to dissect human bodies. This is understandable, but it is much less understandable to us that these errors were not noticed before the sixteenth century. Vesalius made it clear that the reason for this was precisely the slavish adherence to ancient authority that was now rejected by Vesalius and other Renaissance thinkers:

Contemporary anatomists are so firmly dependent upon I-know-not-what quality in the writing of their leader that, coupled with the failure of others to dissect, they have shamefully reduced Galen’s writings into brief compendia and never depart from him—if ever they understood his meaning—by the breadth of a nail. Indeed, in the prefaces of their books they announce that their writings are wholly pieced together from Galen’s conclusions and that all that is theirs is his.…So completely have all yielded to him that there is no physician who would declare that even the slightest error had ever been found, much less can now be found, in Galen’s anatomical books, although it is now clear to me from the reborn art of dissection…

A Revolution within a Revolution: The Copernican Revolution

There can be no denying that a major aspect of the Scientific Revolution was the reform of astronomy introduced by Nicolaus Copernicus (1473–1543) in his De revolutionibus orbium coelestium ( On the Revolutions of the Heavenly Spheres , 1543). Although its impact was at first limited to the technical community of astronomers, it eventually led not only to a revised cosmology, but also to a revised physics. It is easy to see that this too followed upon the Renaissance voyages of discovery, and the re-discovery of ancient philosophy. The very first chapter of Copernicus’ book affirms that the Earth is a single terraqueous globe, as described in Ptolemy’s Geography ; problematic as Copernicus’ theory was for his contemporaries, he must have recognized that it was easier to claim Ptolemy’s terraqueous globe was in continual motion than to claim that a sphere of water, in which the sphere of the Earth was floating with one hemisphere above the surface of the water, was in continual motion.

But if Ptolemy’s Geography made it easier for Copernicus to defend his position, it was the re-discovered ancient writings that inspired him to forge that position. It was well known that the technical astronomical account provided in its most complete and useful form by Ptolemy in the Almagest (as it was known based on the title given by Islamic scholars from whom it came to the Latin West) was not really compatible with the nested homocentric spheres which constituted the Aristotelian cosmos. Ancient cosmology took it for granted that heavenly motions were perfectly circular, perfectly uniform (that is to say the motions maintain a constant speed), and centred on the Earth. In fact, as we now know (thanks to discoveries made during the Scientific Revolution), the planets speed up and slow down as they, along with the Earth, orbit the Sun, and their orbits are elliptical not circular. Ptolemy’s mathematical ingenuity enabled him to describe a set of values defining the motions for each of the planets which, for the most part, conformed to uniform circular motions. But the planetary motions had to be envisaged not as centred on the Earth, but as moving on imaginary circles, called epicycles, which in turn moved in circles around a larger circle, the deferent, which encircled the Earth, although centred on a point in space some distance away from the Earth.

It was by no means clear to astronomers, much less to philosophers, whether Ptolemy’s eccentric wheels within wheels could be considered compatible with the simple homocentric cosmology. Furthermore, Ptolemy’s account did not offer a coherent system, but merely a set of values for dealing with each planet in turn. For Copernicus, the result was what we might recognize as a Frankenstein’s monster. It is, he wrote,

just like someone taking from various places, hands, feet, a head, and other pieces, very well depicted, it may be, but not for the representation of a single person; since these fragments would not belong to one another at all, a monster rather than a man would be put together from them.

Copernicus took it upon himself to provide a new astronomy which was compatible with cosmology, but in so doing he had to change not only astronomy but cosmology as well. It seems clear that he took it upon himself to do this, at least in part, because he wished to restore what he saw in ancient writings as a close alliance between astronomy and cosmology, before Ptolemy forced them apart. We need not go into the complexities, and anyway Copernicus was not entirely successful because he too clung to the premise that heavenly motions must be uniform and perfectly circular, but by putting the Earth among the planets he arrived at a system in which the order of the planets from the Sun could be established by geometry, and that order coincided with the order suggested by the lengths of the planetary orbits (Mercury’s being the shortest, Saturn’s the longest). The order was not new (except for the fact that the Earth was now in between Venus and Mars, the position previously occupied by the Sun)—the length of orbit had been used by Ptolemy to provide the order of the planets, but this was merely conventional, and Ptolemy had no other means of confirming the order. The conformity of Copernican geometry with the conventional order was sufficient to convince Copernicus that his theory was correct. Few of his immediate contemporaries saw it the same way, however. After all, a geometrical nicety, essentially an aesthetic point about the conformity of geometry with tradition, is a small thing to weigh against the extraordinarily unlikely claim that the Earth is in motion.

Ptolemaic astronomy was in such disarray by the sixteenth century (its inaccuracies having accumulated over the centuries) that astronomers eagerly embraced Copernicus’ new system. For the most part, however, they continued to believe it was incompatible with Earth-centred cosmology, and saw it just as an improved mathematical model with no basis in truth. Even so, the new attitude towards observation, and testing age-old claims against physical reality, made other inroads into astronomy and cosmology. The leading astronomer, Tycho Brahe (1546–1601), believed that accurate observations would enable the reform of astronomy without having to assume the motion of the Earth. A wealthy member of the Danish nobility, he equipped his palace, Uraniborg, with impressive sighting devices and other astronomical instruments, and established himself as an observer of unprecedented accuracy. But he was also fortunate enough to witness the rare event of what is now called a supernova (an exploding star) in 1572. Visible even in daylight, the phenomenon had to be regarded by Aristotelian thinkers as atmospheric. But Tycho took it upon himself to measure the parallax of this new light in the sky—such measurements enable an estimate of the distance from Earth, and so could establish whether this was a sublunar, or a heavenly, phenomenon. Tycho was able to establish, beyond doubt, that this was indeed a new star in the heavens. He subsequently used the same techniques to establish that comets, which again he was lucky enough to be able to observe with the naked eye (telescopes were not yet invented), were also located above the Moon. These results were highly significant because they disproved the Aristotelian claim that the heavens are perfect and unchanging, and that, consequently, new stars are impossible, and comets, like meteors, must be atmospheric (or meteorological) phenomena, taking place below the Moon.

The culmination of this kind of astronomical observation was reported in Galileo’s Siderius nuncius ( Message from the Stars , 1610), following his use of the telescope, an instrument which had recently been invented in the Netherlands for commercial purposes. Galileo (1564–1642) reports seeing effects which suggested to him that there are seas, mountains, and valleys on the Moon, and that it is, therefore, not merely an aetherial light in the sky, but is a massive body exactly like the Earth. Galileo left unsaid the implication that if this massive body can be acknowledged by everyone to be moving through the heavens, then the same could be true of the Earth. Galileo also showed that Jupiter has its own satellites, just as the Earth has its Moon. Again, this was important because the Earth seemed anomalous in the Copernican system (in which everything went around the Sun, except for the Moon). Finally, Galileo showed that there are innumerable stars which are invisible to the naked eye and only become visible when viewed through a telescope. This addressed another objection to the Copernican theory. According to the new theory the stars must be inconceivably farther away from the Earth than in the old geostationary world system because they show no parallax—that is to say, they show no movement when observed six months apart, or when observed from opposite sides of the Earth’s vast orbit. In response to this, supporters of Copernicus had already introduced the suggestion that perhaps the universe is infinite in extent, with the stars scattered through it; Galileo’s telescopic view of many more stars than were visible to the naked eye gave more credence to this view.

Galileo took the Copernican theory out of the hands of a few specialist astronomers and a few maverick natural philosophers, and brought it to the attention of all educated readers. Furthermore, his determination to show the truth of Copernican theory led him into conflict with his church, a cause célèbre which made the Copernican theory impossible to ignore. But Galileo’s arguments in support of Copernicanism were complemented by the careful and ground-breaking mathematical astronomy of Johannes Kepler (1571–1630). Using Tycho’s extremely accurate observations of Mars, and believing he should not be satisfied with approximate agreement (because he believed Tycho had been sent by God to help him reform astronomy), Kepler eventually broke with the tradition of celestial circularity and established that the planets move in ellipses, and speed up and slow down in a predictable way as they perform their orbits. The seal was finally set upon Kepler’s work when Isaac Newton (1642–1727) showed, in his Principia mathematica (1687), that these planetary movements followed from the universal principle of gravitation.

Copernican theory had implications far beyond astronomy. We have already seen that it led to theories of infinite space, but this in turn led to new speculations about the possibility of void space, or vacuum. Aristotle rejected the existence of vacuum as a contradiction in terms, but the vastness of space between the orbit of Saturn, the outermost planet, and the nearest stars, which Copernican theory demanded, suggested that the space must simply be empty. Accordingly, the possibility, or not, of vacuum became a growth area in natural philosophy after Copernicus. The first air-pump, for creating artificial vacua, was invented in 1650 by the Burgomaster of Magdeburg in Germany, Otto von Guericke (1602–86). Experiments with air-pumps soon took on a life of their own and led to major reforms of scientific knowledge in a number of areas, but the fact remains that this experimental research grew out of the Copernican revolution. Guericke makes it perfectly clear in his book, Experimenta nova … de vacuo spatio ( New Experiments on Empty Space , 1672) that his main concern in beginning his experiments was to provide support for the Copernican theory. Remarkably, Guericke also invented the first generator of static electricity (a ball of fused sulphur which developed a static charge when rubbed) to provide further evidence in favour of Copernicus. Guericke showed how his sulphur globe attracted various small objects which then remained on its surface as the globe was spun round. ‘Now we can see’, Guericke wrote, ‘how the sphere of our Earth holds and maintains all animals and other bodies on its surface and carries them about with it in its daily twenty-four hour motion.’ The electrical phenomena Guericke described attracted immediate attention and, again, led to major new understandings of the natural world, but these new developments also arose initially from Copernicanism.

The importance of the Copernican stimulus to a new understanding of space—infinite and empty—can be seen in Isaac Newton’s concept of absolute space. Newton’s laws of motion presented in his Principia mathematica are only valid on the assumption that there is a real, unchanging, non-interacting, infinite empty space which provides the arena in which all bodies move and act upon one another. Unlike Aristotelian space, in which there are so-called natural places for each of the five elements, and in which natural movements are completely different in different regions (straight line, up and down, natural motions below the Moon; circular natural motions above it), Newton’s space has to be everywhere the same throughout its infinite expanse, undifferentiated and unaffected by the bodies in it, in short an absolute space. When Newton wrote his Mathematical Principles of Natural Philosophy he began by defining the technical terms and concepts he was about to use. In spite of the crucial importance of the notion of absolute space to his physics, however, he did not have to define it. ‘I do not define absolute space’, he simply wrote, ‘as being well known to all.’ By 1687 it was indeed well known (although not unanimously accepted—some natural philosophers still held out for a notion of space as only relative to the bodies occupying it), but only as a result of the up-take of the Copernican theory, and the demands of this system for a reform of previous views of space.

Moreover, the Copernican theory led to new work on the theory of motion. According to Aristotle, nothing can move unless it is moved by something, and if the mover ceases to operate, the motion will also cease. But if the Earth is in motion, as Copernicus says, what keeps it in motion? This became a major problem for supporters of Copernicus. William Gilbert (1544–1603), a London-based physician and would-be reformer of natural philosophy, hit on the idea of using magnetism to explain the motion of the Earth. Realizing from the work of earlier students of magnetism that the Earth itself was a giant magnet, Gilbert argued that since magnets can spontaneously move themselves, they must have a soul—Aristotle himself had conceded that animate things could move themselves—and if the Earth is a magnet it must have a soul, and so can move itself. Gilbert’s animistic ideas were embraced by later thinkers, though usually only after turning his notion of the magnetic soul into some sort of magnetic force or principle (no longer seen as animate, merely occult). Kepler adopted this idea to explain how planets can move in ellipses, and his theory of a magnetic force operating between the Sun and the planets was easily replaced in Newton’s Principia mathematica by the attractive force of gravity. Galileo, meanwhile, was developing his own account of how the Earth kept in motion, and his theory can be seen to lead, culminating again in the work of Newton, to the principle of inertia. This principle rejects the Aristotelian necessity for a continual mover, arguing that once movement is initiated it will continue until something intervenes to stop it. Galileo believed that such perpetual motion needed to be circular—once something is set in motion in a circle it will continue to move that way indefinitely. But Descartes and others pointed to motion in a straight line as the natural form of motion, and Newton set the seal upon it, and simultaneously showed that planetary motions could only be deviated from motion in a straight line and bent around into an ellipse as the result of a continuously acting force—gravity. Although Galileo was wrong about inertial motion, he had much better luck with his associated experimental investigations of free fall, and was able to replace the Aristotelian assumption that bodies fall faster the heavier they are with his law of free fall which states that all bodies fall (disregarding any interference from the medium through which they fall) at the same rate.

Replacing Aristotle: From Occult Philosophies to the Mechanical Philosophy

Copernicanism was not the only innovation to have such wide-ranging consequences. Dissatisfaction with the Aristotelian system, accumulating as a result of scholarship based on ancient alternative philosophies and increasing discoveries that revealed the fallibility of his system (from confirmation of the terraqueous globe to the appearance of the new star in 1572, and so forth), led to increasingly cynical dismissals of his natural philosophy.

This included a rejection of his hylomorphic theory of matter and the concomitant attempt to explain all material phenomena in terms of the four (so-called) manifest qualities of hot, cold, dry, and wet. Hylomorphism refers to the Aristotelian assumption that bodies are made of matter ( hyle ) and form ( morphe )—matter cannot exist without form (try imagining a lump of matter which has no shape whatsoever); and it makes no sense to talk of the form of nothing, so form has to be imposed on some matter. To explain the countless different varieties of body (from metal, to wood, to fluff, or vapour and beyond), Aristotle took a reductionist line and assumed that all could be explained in terms of different combinations of four elements (earth, water, air, and fire). These four elements embodied four fundamental, irreducible, qualities (fire was hot and dry; earth, cold and dry; water, cold and wet; air, hot and wet). Aristotle wished to explain all the changes of bodies in terms of these four manifest qualities—that is to say, four qualities which were obvious and easily detected by the senses (especially by touch). Unfortunately, Aristotle was forced to recognize that not all properties of bodies could be reduced to these four qualities. Although something smooth, for example, could be assumed to have water in its composition—since wetness seemed to the touch to correlate with smoothness; and a drink that made one hot must have air or even fire in its composition—what could we say about a magnet’s ability to attract a piece of iron? This ability did not seem to be explicable in terms of any of the four qualities. Wetness might account for stickiness, and so the adherence of the iron to the magnet might be seen as the result of a binding wetness, but what made the iron move towards the magnet? In some cases fire seemed to draw things towards it—air and other light things—but no fire could pull in a piece of iron. There was nothing for it but to accept the evidence provided by experience that magnets had an occult quality, and this quality could not be reduced to the manifest qualities.

Aristotle, and his medieval scholastic followers, avoided recourse to occult qualities as much as possible—seeking to explain everything in terms of the manifest qualities. But Renaissance philosophers found themselves increasingly resorting to occult qualities. Medicinal plants were said to operate by their manifest qualities. Some plants were cooling (either when eaten, or when applied as a poultice) and could be used to combat fever; others were sudorific or diuretic and could be used to dry out someone who was judged to be suffering from an excess of moisture in their system. But plants that were known in the local lore of a particular region to have healing effects, but which were not mentioned by Aristotle or his ancient follower and specialist in plants, Theophrastus ( c .371– c .287 bc ), or the later Dioscorides ( c . ad 40–90), could not always be seen to work by one of the manifest qualities. This was exacerbated by the increase of medicinal plants brought into Europe from the New World. Where there was no ancient authority to indicate how a plant exerted its healing effect, natural philosophers increasingly resorted to occult qualities.

Subsequently, the most ambitious Renaissance philosophers tried to develop their own systems of natural philosophy, which they hoped would replace the increasingly untenable Aristotelian system. At first, these would-be replacement systems all relied heavily upon occult principles. Presumably, these innovators had all noticed the increasing usefulness of occult qualities, and saw them as an under-exploited aspect of Aristotelianism, which potentially could be used as the basis for a new philosophy. This new attitude to the occult was undoubtedly encouraged by the re-discovery of ancient writings attributed to the Greek god, Hermes Trismegistus (who was assumed to be a real sage, whose wisdom had been acknowledged to be so great that he had been deified by the ancients). Although essentially Neoplatonic, and therefore rather religious in tone, these re-discovered writings were linked to various alchemical and other magical texts which were also attributed to Hermes Trismegistus. The result was that secular Renaissance thinkers were able to overcome the strictures of the Church against magic (which for the Church was always associated with the activities of demons), and claim that natural magic (a magic based not on demonic activity but on the natural occult powers of things—occult powers bestowed upon these things by God at the Creation) was part of the oldest wisdom known to man. Underlying these claims was a belief that Adam had known all things, and that after the Fall, his wisdom was successively forgotten from generation to generation. But the further back in time the scholar could go, the closer he came to recovering Adamic wisdom. Hermes was widely seen, in the Renaissance, as a contemporary of Moses, and a pagan sage who had not yet forgotten everything Adam had known.

The first translator of the Neoplatonic Hermetic writings from Greek into Latin was Marsilio Ficino (1433–99), who developed his own occult system of philosophy, De vita ( On Life , 1489). This proved to be extremely influential and inaugurated a vogue among the most ambitious Renaissance thinkers for developing alternative systems of philosophy. At first all those who attempted to develop alternative new philosophies relied to a greater or lesser extent on occult or magical approaches. The leading figures here include Giovanni Pico della Mirandola (1463–94), Pietro Pomponazzi (1462–1525), Cornelius Agrippa (1486–1535), Paracelsus, Girolamo Fracastoro ( c .1477–1553), Jean Fernel ( c .1497–1558), Girolamo Cardano (1501–76), Bernardino Telesio (1509–88), Francesco Patrizi (1529–97), Giordano Bruno (1548–1600), William Gilbert (1544–1603), Francis Bacon (1561–1626), and Tommaso Campanella (1568–1639). Jean Fernel took up a position that was close to Aristotelianism but with a much greater role allowed for occult qualities. Francesco Patrizi, by contrast, rejected Aristotelianism almost entirely and developed a philosophy which was much closer to Neoplatonism. Others took up positions somewhere along the spectrum between occult Aristotelianism and more Ficinian Neoplatonism. Although some, such as Fernel and Paracelsus, proved influential and gathered followers, none of them were able to persuade the majority of their educated contemporaries that they had arrived at the true philosophy, worthy of replacing Aristotelianism.

Then, at the beginning of the seventeenth century, a new and powerful alternative to occult philosophies emerged. It is possible this radically different approach arose from modes of thought that were comparatively common among mathematical practitioners, but the state of historical research at present only allows us to say that two leading mathematical thinkers independently developed an entirely kinematic approach—that is to say, they tried to explain all physical phenomena exclusively in terms of bodies in motion. These two radical innovators were Galileo Galilei and René Descartes (1497–1650). There was a third innovator who developed a kinematic physics, Isaac Beeckman (1588–1637), and he actually introduced Descartes to this new way of doing physics, but unlike Descartes, he never fully developed his natural philosophy and never published his ideas, so he had no subsequent effect on developments (except indirectly, through Descartes). A fourth thinker who tried to develop an entirely kinematic physics was Thomas Hobbes (1588–1679), but his system of physics was a derivative combination of ideas from Galileo and Descartes.

Galileo was as robustly opposed to magical ways of thinking as he was to Aristotelianism, and it looks as though he conceived the possibility of developing a kinematic physics when he realized that Copernicus’ moving Earth might provide an explanation of the tides—an explanation which did not involve the occult influence of the Moon. The association between the Moon and the tides had been known since ancient times and was assumed to be due to occult influence. A moving Earth, however, suggested to Galileo that the oceans might be slewing about as the Earth rotates (the details are complex but Galileo drew an analogy with the fresh water brought across the lagoon to Venice in barges—if a barge’s motion changed, the water would shift and rise up either at the front or the back of the barge). Galileo’s investment in this idea was so great that he even saw the tides as proof that the Earth must be in motion, as Copernicus said. Accordingly, he made his theory of the tides the mainstay of his attempt to prove the truth of Copernican theory in his Dialogue on the Two Chief World Systems (1632)—this was the same work in which he introduced the idea, mentioned earlier, that once a body is set moving in a circle it will continue to do so indefinitely, unless something stops it (again, this was crucial for his kinematic physics). In his final work, Discourses on Two New Sciences (1637), he developed his kinematics further, and even contrived to explain acceleration in free fall without recourse to the occult idea of gravity (by restricting discussion of acceleration due to gravity to the fact that ‘equal increments of speed’ are given to the body—there is no discussion as to why the speed increases).

Meanwhile, the French mathematician, René Descartes, had developed a much more comprehensive and systematic kinematic physics. Descartes was about to publish this in 1633 when he heard of the condemnation of Galileo by the Inquisition for his promotion of Copernicanism. Since Descartes’s system also depended on the assumption that Copernicus was correct, he suppressed his work, and his fully developed system was not published until 1644, as Principia philosophiae ( Principles of Philosophy ). Descartes’s system is rich and complex, but in its essentials it combined an atomistic philosophy with a physics based on the centrifugal forces generated when a body is made to rotate (think of whirling a stone around in a sling—the stone tends to move away from the centre of rotation). Atomism was one of the ancient philosophies that had been re-discovered by Renaissance scholars, and sought to explain everything in terms of atoms moving, colliding, combining, and dispersing. This may seem close to kinematics, but the most prominent of the revivers of atomism, Pierre Gassendi (1592–1655), for example, assumed that atoms had their own internal energies and principles of movement. Accordingly, Gassendi has been seen as closer to the tradition stemming from Ficino, and his atomism has distinct occult elements built into it. This was not the case with Descartes; if he included unexplained principles of activity in his earliest thinking, he was soon able to excise them and develop a completely kinematic system in which everything was explained in terms of the motions of invisibly small particles, their collisions, and the transfer of motion from one particle to another in those collisions. It was with regard to the transfer of motion that Descartes developed his three laws of nature (the third of which was supplemented with seven rules of collision)—the first explicit statement of precise laws which could then be used to analyse and predict the behaviour of inanimate bodies.

Galileo’s and Descartes’s attempts to develop systems of philosophy which did not rely on occult principles were immediately recognized as potentially useful, and proved highly influential. Cartesianism came to be known as the mechanical philosophy because all physical change was explained in terms of the intermeshings, friction, and collisions of material parts. Descartes even extended this to living things, so that plants and animals (and even human bodies—though he did acknowledge the existence of an immortal soul in humans) were seen to be like automata. This represented a major change in theories of life. For Aristotle only living things were capable of self-movement (including growth in the case of plants), and this ability denoted the presence of a soul in the self-moving, living thing (albeit merely a vegetative soul, or an animal soul). But Descartes pointed out that clocks and other automata (he lived in an age when ingenious craftsmen had been able to make remarkable automata) could move themselves, and yet nobody inferred from their movements that they had souls. Descartes dismissed all but the rational, immortal soul of human beings (which he retained on religious grounds), and living things were as much machines as anything else in his mechanical philosophy.

Descartes’s system was so fully worked-out, so comprehensive in its coverage (in principle at least), that it began to supplant Aristotelianism in universities—especially in the Netherlands. In his native France, Cartesianism was perceived as a threat to sound religion and for a while it was proscribed by the Crown, but it seems fair to say that the succeeding generation of French natural philosophers, and in particular those who constituted the newly founded Académie des Sciences in 1666, were predominantly Cartesian. This is not to say that the flaws in Descartes’s system were not noticed (the system was more ingenious than it was workable), but it was undeniably the only system of philosophy which was capable of replacing the fully comprehensive Aristotelian system, lock, stock, and barrel—no other thinker presented a system that even came close. At a time when Aristotelianism was regarded as no longer tenable, Cartesianism was widely regarded as the only philosophical system capable of taking its place.

In Britain, the Cartesian system did not fare so well. Natural philosophy in England was strongly affected by the philosophy of Francis Bacon, the first major philosopher to appear in England since the Middle Ages. Bacon tried to develop his own occultist (it has been described as semi-Paracelsian) natural philosophy but his main impact derived from a programme he developed for reforming natural philosophy. It was always recognized that occult qualities could only be discovered, or understood, as a result of experience: nothing about the appearance of a magnet enables us to predict its effect on iron, but we learn it easily when we see the magnet interacting with a piece of iron. Some of the earlier thinkers in the occult tradition, such as Paracelsus, Fernel, and Cardano, had been explicit about the need to base natural philosophy on experience (and of course this went hand in hand, as we have seen, with the anti-authoritarian aspects of Renaissance thinking), but Bacon was the first philosopher to provide a philosophical defence of experience and a reasoned account of the importance of what became known as the experimental method. This method, and the Baconian approach more widely, was taken up by the succeeding generation of English thinkers, and the new philosophy as it developed in England came to be called the experimental philosophy.

Descartes’s system was for the most part presented as a rationalist philosophy, advancing logically from initial premises. When Descartes did present seemingly experimental evidence, he interpreted it in a way that suited his preconceived doctrines. He appropriated Harvey’s experimental demonstration of the circulation of the blood, for example, but made it serve his own mechanistic conclusion, rather than the more occultist conclusion of Harvey. Harvey’s experiments had clearly shown that the contraction of the heart was its active stroke, and concluded the heart had an unexplained ability to repeatedly contract. This was too occult for Descartes, who insisted the heart was so hot it could explosively vaporize incoming blood from the lungs, thereby inflating the heart and sending the blood out into the great artery. It followed from this that the expansion of the heart must be its active stroke, and Descartes implied that is what Harvey’s experiments showed. Accordingly, English readers of Descartes tended to be suspicious of his work and continued to offer their own experimentally based version of natural philosophy. It was important to English thinkers that their experiments could be presented as being performed in a theory-free way (without theoretical preconception), just as the experimental method had been developed by Bacon in his Novum organum ( New Organon , 1620, echoing the traditional title given to Aristotle’s collected works on logic— Organon ).

The culmination of the English approach can be seen in Isaac Newton’s Philosophiae naturalis principia mathematica ( Mathematical Principles of Natural Philosophy , 1687). Newton’s incomparable abilities as a mathematician enabled him to explain the motions of the planets, as determined by Kepler, on the assumptions that planets seek to move indefinitely in straight lines (the principle of inertia), but are continually attracted to the Sun with a force that varies inversely as the square of the distance between the Sun and the planet (the universal principle of gravitation). Accepting the Baconian tradition, Newton felt no compunction to provide the kind of mechanistic account of how gravity operated on the planets that Cartesians demanded. Cartesians explained gravity in terms of the downward push of continually descending invisibly small particles, but for Newton these supposed streams of particles were hypothetical entities with no evidence that independently verified their existence. Newton’s gravity, like the attractive power of the magnet, was simply confirmed on the one hand by everyday experience, and on the other by the fact that the motions of bodies affected by gravity could be analysed and predicted in terms of Newton’s mathematical laws of nature (which replaced Descartes’s three laws, and proved much more useful). ‘And it is enough’, Newton wrote, ‘that gravity really exists and acts according to the laws that we have set forth and is sufficient to explain all the motions of the heavenly bodies and of our sea.’

It is important to note, however, that English natural philosophers did not have a monopoly on experimentalism. Galileo, whose studies of motion were conducted with carefully designed experiments rolling balls down inclined planes, or with experiments with pendulums, for example, helped to establish a strong experimental tradition in Italy. This is most easily seen in the work of the Accademia del Cimento, founded in 1657 by a number of Galileo’s followers, as an institute for pursuing experimental philosophy. Even in the Netherlands and France, where Descartes’s rationalist philosophy had most success, experimental approaches were used to test his claims. One of the most famous and far-reaching examples of this was the set of experiments performed by Blaise Pascal (1623–62) to establish, contrary to Descartes, the possibility of void space, and the role of atmospheric pressure in various phenomena. Following on from the claims of Evangelista Torricelli (1603–47), a student of Galileo’s, that a column of mercury in a glass tube whose lower end is immersed in a bath of mercury is held up by the pressure of the atmosphere on the surface of mercury in the bath, Pascal reasoned that the lesser atmospheric pressure at the top of a mountain would only be capable of supporting a shorter column. Pascal’s hypothesis was confirmed by conducting experiments during an ascent of the Puy de Dôme in central France, and he went on to assert that the space above the mercury in the tube was a vacuum, publishing the results of this and other experiments in Experiences nouvelles touchant le vide ( New Experiments Concerning the Void , 1647). Experiments on void space were subsequently devised and conducted at the Royal Society by Robert Boyle (1627–91) and Robert Hooke (1635–1703), using an air-pump that was an improvement on Otto von Guericke’s, so it is clear that, from Torricelli to the Royal Society via Pascal and Guericke, experimentalism was a European movement.

Attempts to replace the Aristotelian system, then, began with recourse to occult notions and philosophies of nature that were based to differing extents on assumptions about the occult qualities and powers of things. From Fracastoro’s De sympathia et antipathia rerum ( On the Sympathy and Antipathy of Things , 1546) to Newton’s declared aim in the preface of the Principia to explain all phenomena in terms of ‘certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled toward each other…or are repelled and recede from each other’, natural philosophers tended to assume that bodies had unexplained (though God-given) principles of activity which accounted for many of the phenomena of nature. Within this larger picture we can see the efforts of Galileo, Beeckman, Descartes, and Hobbes to rescind all use of unexplained powers and principles of activity and to invoke only passive bodies in motion as their explanatory principles. This exclusively kinematic movement ultimately failed (although Descartes had many followers into the eighteenth century), but it was powerful enough to change the character of the more occult and dynamic natural philosophies. Where newly proposed natural philosophies before Galileo and Descartes were overtly occult, afterwards the new philosophies tended to be dynamic versions of mechanistic philosophy, in which assumptions about the unexplained powers and active principles of things were justified in terms of experience. Although writing in the preface to the Principia about gravitational attraction, an action at a distance that neither Galileo nor Descartes could have accepted for a moment, Newton still felt able to present it as part of mechanical philosophy: ‘I wish we could derive the rest of the phaenomena of Nature’, he wrote, ‘by the same kind of reasoning from mechanical principles.’

The New Philosophies and Society: Patronage and Pragmatism

Intellectual developments, no matter how recondite and abstruse, do not take place in a vacuum, with no reference to anything but other intellectual developments. In the foregoing account, even though we were focusing primarily upon intellectual developments, to understand those developments we had to allude to the wider context, starting with the broad context of the set of historical changes known as the Renaissance. But there were a number of more specific social and political changes which made the Scientific Revolution what it was.

If the rise of magic was made possible by its newly acquired respectability after the recovery of the Hermetic corpus, its adoption in practice owed more to its promise of pragmatic usefulness than to any Hermetic doctrines. The same concern for the pragmatic uses of knowledge can be seen in the increasing attention paid by scholars and other elite groups to the techniques and the craft knowledge of artisans. The increasing importance of mining and metallurgy in the economy of Europe, for example, drew the attention of practically minded intellectuals. The first printed account of Renaissance mining techniques, including instructions on the extraction of metals from their ores, how to make cannons, and even how to make gunpowder, was the De la pirotechnia (1540) of Vanuccio Biringuccio (1480–1539). Written in Italian by a mining engineer who rose to the rank of director of the papal arsenal in Rome, it was evidently intended as an instruction manual for others working in similar circumstances to Biringuccio himself. This can be compared with the De re metallica (1555) of Georgius Agricola (1494–1555). Agricola was a humanist scholar who taught Greek at Leipzig University before turning to medicine. Practising in a mining area, and initially interested in the medicinal uses of minerals and metals, he soon developed a compendious knowledge of mining and metallurgy. The fact that the De re metallica was published in Latin shows that it was aimed at an audience of university-trained scholars, not at miners or foundry-workers. Furthermore, the book’s numerous editions and wide dissemination throughout Europe show that Agricola did not misjudge the audience.

Similar stories could be told in other areas. Although only a potter, Bernard Palissy’s (1509–90) efforts to reproduce Chinese porcelain made him famous. He was able to give public lectures in Paris on topics in what we would think of as mineralogy, geology, hydrology, and agriculture. In 1580 he published his fund of knowledge in Discours admirables , never missing an opportunity to extol the virtues of practice over theory. The introduction of the magnetic compass, one of the major practical innovations of the Renaissance to rank alongside printing and gunpowder, effectively led to a new science of magnetism. It was noted that compass needles did not simply point north, and various attempts were made to put their other movements, notably variation and declination, to use for determining longitude, or latitude when cloud or fog obscured the heavens. Here, for example, the discovery of declination by a retired mariner and compass-maker, Robert Norman ( fl . 1590), was taken up and expounded by William Gilbert in the first thorough study of electrics and magnetism, De magnete ( On the Magnet ) of 1600.

Other scholars remained content with talking in general terms of the importance of craft knowledge. The Spanish humanist and pedagogue, Juan Luis Vives (1492–1540), acknowledged the importance of trade secrets in his encyclopaedia, De disciplinis ( On the Disciplines , 1531). Francis Bacon, similarly, wanted to include the knowledge and techniques of artisans in a projected compendium of knowledge which was to form part of his Instauratio magna ( Great Restoration ), a major reform of learning. Bacon’s influence in this regard can be seen not only in various groups of social reformers in England during the Civil War years and the Interregnum, but also in the Royal Society of London for the Promotion of Useful Knowledge, one of the earliest societies devoted to acquiring and exploiting knowledge of nature. The Society made a number of repeated attempts, using specially produced questionnaires, to ask its members to return information about local craft techniques and artisans’ specialist knowledge in and around their places of residence. The idea was to produce a ‘history of trades’ to supplement the usual natural histories.

We have already mentioned the role of secular patrons in stimulating the arts, and in effectively promoting the re-discovery of ancient philosophies other than Aristotle’s, by establishing personal libraries and employing scholars to build them up. During the Middle Ages the only patron for major paintings was, effectively, the Church, and this inevitably showed in the subject-matter and style of the resulting paintings. Secular patrons, however, wanted (sometimes at least) secular subject-matter and more realistic representations—and the resulting effect on the art of the Renaissance is wonderfully obvious. But secular patrons also affected the way the natural world was studied, and how that knowledge was put to use. Essentially, the concern of the secular patron was with the pragmatic usefulness of knowledge, although in some cases that usefulness might amount to nothing more than the aggrandizement of the patron—a confirmation of his wealth and power.

The earliest groupings of investigators of nature all seem to have been brought together by wealthy patrons, particularly by sovereigns and princes. Indeed the royal courts must have been one of the major sites for bringing together scholars and craftsmen, which we have already seen was one of the characteristic features of the Scientific Revolution. The amazingly elaborate court masques and festivals conceived in order to publicly display the magnificence and glory of the ruler required a huge team of facilitators. Learned scholars would devise appropriate themes, combining traditional notions of chivalry and honour with more fashionable lessons taken from newly re-discovered classical stories, while architects and engineers would design the elaborate settings intended to illustrate the moral themes and a vast array of other artisans and craftsmen would be brought together to make it all a breath-taking physical reality. It is hard to imagine a comparable site during the period for the creative collaboration of scholars and craftsmen. Unless, of course, it was one of the many sites where the arts of war demanded such collaborations.

If festivals and wars were only occasional affairs, the offer of more long-term patronage to alchemists and other natural magicians, engineers, mathematicians, natural historians, and natural philosophers was obviously done with the aim of increasing the wealth, power, and prestige of the patron. Usually this meant that the patron was most concerned with some practical outcome from the work of these servants of his court. Even in the case of seemingly more remote and abstract physical discoveries, it is possible to see such practical concerns in the background. When Galileo, professor of mathematics at the University of Padua, discovered the moons of Jupiter with his telescope and named them the Medicean Stars, after the ruling Medici family of Florence, he was bargaining for patronage by offering celestial and quasi-divine significance to Duke Cosimo, as well as putting him onto the star maps. But he did not stop there. By trying to produce tables of the motions of the moons of Jupiter, which he hoped would provide a means of determining longitude at sea, Galileo was potentially turning his discovery into one of the utmost practical benefit, from which the Medici could hardly fail to gain.

Mathematical practitioners in general tended to benefit from the pragmatic interests of secular patrons. The result was a rise in social and intellectual status which enabled mathematicians to make bolder claims for their subject than was previously possible. Mathematics was held in low regard by Aristotle, who insisted that natural knowledge must be grounded on causal explanations—if the causes of a phenomenon were known then that phenomenon was properly understood. Mathematical analysis of a particular phenomenon or set of phenomena could not offer the kind of causal explanations demanded by Aristotle and his later scholastic followers and so was regarded as of little use to contemplative natural philosophy. The more pragmatic concerns of secular patrons, however, could often benefit from mathematical analysis. Furthermore, mathematicians could also legitimately claim that their results were usually certain and therefore reliable—which could seldom be said for results acquired through Aristotelian speculation.

A new confidence in mathematics can be seen, for example, in Copernicus’ presentation of his new astronomical and cosmological theory. Although Copernicus could offer no explanation at all as to how the Earth could move, he was convinced nevertheless of the physical truth of his theory. It was as if Copernicus was willing to accept the truth of his theory not, as an Aristotelian would have demanded, on physical and causal grounds, but simply because the mathematics pointed to its truth (by providing a geometrical demonstration of the order of the planets which fitted the order suggested by planetary periods, and by explaining how all the planets seemed to incorporate in their own motions the annual motion of the Sun—since this was actually the annual motion of the Earth, projected, as it were, onto each planet). When Copernicus published his De revolutionibus in 1543, not all mathematicians had such confidence in the power of their own discipline, but by the time Newton published his demonstration of the Mathematical Principle of Natural Philosophy in 1687, the battle had been won, and mathematical approaches to an understanding of the physical world have been regarded as essential ever since. Although Copernicus was not himself in the employ of a wealthy patron with pragmatic concerns, it seems hard to deny that his confidence in the power of mathematics was affected by the general increase in status of mathematics and mathematicians that was a major outcome of secular patronage in the Renaissance.

The political potential of natural knowledge was a major reason for Francis Bacon’s concern to reform the means of acquiring knowledge and of putting it to use, as described in his various programmatic statements and illustrated in his influential utopian fantasy, New Atlantis (1627). The most prominent feature of Bacon’s utopia is a detailed account of a research institute, called Salomon’s House, devoted to acquiring natural and technological knowledge for the benefit of the citizens. Bacon repeatedly sought patronage for his so-called ‘Great Instauration’, first from Elizabeth, then from James I, although neither were to agree to it (even though Bacon did become, briefly, James’s Lord Chancellor). But Bacon’s posthumous fame was such that Charles II of England and Louis XIV of France did recognize the political potential of enhanced knowledge of the natural world and offered their patronage to what were to become the leading scientific societies in Europe, both of which were explicitly modelled on Salomon’s House. In the French case at least, thanks to Jean-Baptiste Colbert (1619–83), the controller general of finance, the Académie Royale des Sciences (1666), with its salaried fellows, can be seen effectively as an arm of the State. The Royal Society, founded in the year of the Restoration of the English monarchy (1660), never gained more than nominal support from an administration that was preoccupied with more pressing matters. It had to be much more apologetic, therefore, in its attempts to demonstrate its usefulness to the State. Even so, it can be seen from the propagandizing History of the Royal Society of London (1667), by Thomas Sprat, and other pronouncements of the leading Fellows that the most committed members of the Society, at least, saw their experimental method as a means of establishing truth and certainty and so ending dispute in philosophy. This, in turn, was presented as a model which could be used to bring an end to the religious disputes which had divided England since before the Civil Wars, and to establish order and harmony in the State. The existence, to say nothing of the success, of the Académie and the Royal Society shows that the new natural philosophy was far more directly concerned with political matters than the natural philosophy of the medieval period.

But these were by no means the only new institutions devoted to the study of the natural world. Indeed, Bernard de Fontenelle (1657–1757), secretary of the Académie Royale des Sciences from 1697, referred to a ‘new Age of Academies’. In some cases the group was called together by a wealthy patron with an interest in natural knowledge and its exploitation. One of the earliest of these was the group of alchemists, astrologers, and other occult scientists brought together at the court of Rudolf II (1552–1612) in Prague; another was the Accademia dei Lincei (Academy of the Lynxes), founded by the marchese di Monticello, Federico Cesi (1585–1630). The evident attractiveness of such collaborative enterprises can also be seen in the astonishing interest shown by scholars all over Europe in the Brotherhood of the Rosy Cross, whose intended reforms of learning, based on alchemy, Paracelsianism, and other occult ideas were announced in two manifestos which appeared in 1614 and 1615. In fact, to the disappointment of those like René Descartes (1596–1650) who tried to make contact with them, the Brotherhood seems to have been as fictitious as Bacon’s Salomon’s House. The manifestos were written by a theologian and alchemist, Johannes Valentinus Andreae (1586–1654), seemingly as a clarion call to like-minded reformers; but he seems to have rapidly abandoned the idea of making the Brotherhood into a reality when he saw the nature of the interest it generated. If Rosicrucianism came to nothing, however, Bacon’s vision, as we have already seen, was to have a profound effect.

The self-consciously reformist attitudes of the early scientific societies, and their public pronouncements of their methods and intentions in journals and other publications, mark them out as completely different from the universities. It used to be said that the universities during this period were moribund institutions, completely enthralled by traditional Aristotelianism, and blind to all innovation. This has now been shown to be completely unjustified, and the important contributions of some members of university Arts and Medical Faculties to innovation in the natural sciences has been reasserted. Nevertheless, it seems fair to say that it was usually individual professors who seemed innovatory, not the institutions to which they belonged. If there were exceptions to this it was in the smaller German universities, where the local prince might hold greater control over the university by his patronage. A number of such universities introduced significant changes in their curricula. In particular, the introduction of what was known as chymiatria or chemical medicine (embracing Paracelsianism and rival alchemically inspired forms of medicine) as a new academic discipline radically transformed a number of German universities. Similarly, interest in the potential practical benefits of natural magic and other forms of occult philosophy at the Kassel court under Moritz of Hessen-Kassel (1572–1632) led to the appointment of occultist professors at the University of Marburg, not just in the Medical Faculty, where chymiatria became prominent, but in all the other faculties as well. Even so, for the most part it remains true to say that the European universities in general seemed slow to change and institutionally committed to traditional curricula, even if individual professors might seem innovatory. In the case of the new academies or societies, however, the institutions themselves were innovatory, and they had a much greater effect on changing attitudes to natural knowledge.

Another important feature of the interest of wealthy patrons in natural marvels was the development of what were called cabinets of curiosities, collections of rarities and oddities from the three kingdoms of nature: mineral, vegetable, and animal. Originally envisaged, perhaps, as nothing more than spectacles symbolizing the power and wealth of the collector, the larger collections soon came to be seen as contributing to natural knowledge, providing illustrations of the variety and wonder of God’s Creation. Cabinets of curiosities became, in the phrase of Samuel Quiccheberg (1529–67), overseer of the Wunderkammer of Albrecht V of Bavaria (1550–79), theatres of wisdom. Quiccheberg’s plan for organizing such collections was published in 1565 as the Inscriptiones…theatri amplissimi , and proved influential among curators of cabinets for over a century. The curator of Archduke Ferdinand of Tyrol’s (1529–95) collection, Pierandrea Mattioli (1500–77), became one of the leading naturalists of the age. Focusing particularly on the botanical specimens in the collection, Mattioli greatly superseded the work of the ancient authority on botany, Dioscorides, in his influential Commentaries on Dioscorides (1558). Part of the success of this work derived from the accurate illustrations, supplied by craftsmen also under Ferdinand’s patronage.

The larger and more successful collections soon became early tourist attractions, drawing gentlemanly visitors on their ‘Grand Tours’. Perhaps more significant for the spread of natural knowledge was the fact that acquisition of new specimens for the collections demanded extensive networks of interested parties communicating with one another about the latest discoveries and where to acquire them. Eventually, of course, these collections and their obvious pedagogical uses were to inspire the formation of the more publicly available botanical gardens, menageries, and museums. Indeed in some cases, the larger collections formed the nucleus of the first public museums. The collection of the Tradescant family, acquired by Elias Ashmole (1617–1692), formed the nucleus of the Ashmolean Museum in Oxford, while Sir Hans Sloane’s (1660–1753) collection provided an impressive beginning for the British Museum in London.

The New Authority of Natural Philosophy

The historical record strongly suggests that modern atheism appeared in the late sixteenth century—certainly the word was coined at this time—and it is usually attributed to the revival of ancient scepticism (and other effectively atheistic ancient philosophies, such as Epicureanism), to the fragmentation of the Christian Churches (and the concomitant weakening of their authority) after the Reformation, and to the rise of the new philosophy. However, the role of natural philosophy in the decline of religious belief is by no means clear and simple. Certainly, there was no intrinsic reason why any of the new natural philosophies should have turned contemporaries away from religious belief. There can be no denying, however, that those who were disposed towards atheism were easily able to, and did, appropriate the latest thinking about the natural world, and used it to serve atheistic purposes.

As a result of the ‘Galileo affair’, as it was known to contemporaries, the Copernican theory is often seen as emblematic of the supposedly inimical relations between science and religion. But, the Roman Catholic Church took no measures against the Copernican theory, which had been published in 1543 and dedicated to the Pope, until 1616, when it made a hasty ruling against it. The perceived need to make this ruling arose because of what the Church authorities in Rome saw as embarrassing public controversy between Galileo and his enemies. The subsequent development of the affair can also be seen to owe more to Galileo’s tactless unconcern for scoring points off his rivals and turning them into implacable enemies than it did to any supposed enmity between science and religion. Certainly, the circumstances leading to Galileo’s condemnation were so unique and specific to him and his actions that no general conclusion should be drawn about any supposed incompatibility between the scientific approach and religion. Galileo was not condemned for being a Copernican, he was condemned for writing a book promoting it when he had (allegedly) promised the Congregation of the Index (the Inquisition) that he would never discuss it.

Indeed, if we consider all the major contributors to the Scientific Revolution, it is easy to see that they were usually devout believers, and in some cases, such as Robert Boyle and Isaac Newton, they even made important contributions to contemporary theology. But no matter how devout the originator of naturalistic innovations might be, contemporaries with their own atheistic agenda could always seize those innovations for their own purposes. Descartes’s conception of specific laws of nature, for example, led him into profound theological speculation. He was aware that inanimate bodies cannot ‘obey’ laws of nature and assumed that the laws must be somehow enacted and maintained by God. It was easy, however, for subsequent generations of thinkers to dismiss what Descartes saw as irremovable theological implications of the laws of nature, and to simply regard the laws as built into a godless nature. But the atheists were too hasty, and even today there are vigorous debates among philosophers of science about the precise status of laws of nature and how they can have meaning. Similarly, although Descartes himself insisted on the reality of the immortal soul, it was easy for his less devout followers to dismiss it, just as he had dismissed the vegetative and animal souls, and to insist that men, no less than the other beasts, were merely machines.

Devout natural philosophers were appalled to see their ideas put to irreligious uses and there was a strong movement towards what is called natural theology—a theology based not on Scripture but on showing what seems to be the intricate design of the natural world, and its dependence, therefore, on a supreme designer and creator. But the momentum of secularization could not be stopped. Natural theology gave rise to what was called deism (accepting, on naturalistic grounds, the existence of a divine Creator but rejecting the validity of Scripture), and weakened the authority of the Churches. Churchmen saw deism as not far removed from atheism, and the history of increasing secularization proved them to be right.

The many successes of the natural philosophers of the Scientific Revolution raised the authority of natural knowledge, and meant that it could be used to rival the long-held authority of the Church. But, scientific knowledge does not speak for itself, any more than Scripture does, and the authority of scientific knowledge was wielded in different ways by different thinkers. Even so, it is a major and final legacy of the Scientific Revolution that, in the succeeding age, the Age of the Enlightenment, it was scientific doctrine, especially Newtonian doctrine, that shaped theory and practice, not just in the natural sciences themselves, but in the new ‘Sciences of Man’, embracing moral, psychological, political, economic, and sociological thought.

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What is the Scientific Revolution?

How is the scientific revolution connected to the enlightenment, what did the scientific revolution lead to.

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Scientific Revolution

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Scientific Revolution is the name given to a period of drastic change in scientific thought that took place during the 16th and 17th centuries. It replaced the Greek view of nature that had dominated science for almost 2,000 years. The Scientific Revolution was characterized by an emphasis on abstract reasoning, quantitative thought, an understanding of how nature works, the view of nature as a machine , and the development of an experimental scientific method .

The Enlightenment , like the Scientific Revolution, began in Europe . Taking place during the 17th and 18th centuries, this intellectual movement synthesized ideas concerning God, reason, nature, and humanity into a worldview that celebrated reason. This emphasis on reason grew out of discoveries made by prominent thinkers—including the astronomy of Nicolaus Copernicus and Galileo , the philosophy of René Descartes , and the physics and cosmology of Isaac Newton —many of whom preceded the Enlightenment.

The sudden emergence of new information during the Scientific Revolution called into question religious beliefs, moral principles, and the traditional scheme of nature. It also strained old institutions and practices, necessitating new ways of communicating and disseminating information. Prominent innovations included scientific societies (which were created to discuss and validate new discoveries) and scientific papers (which were developed as tools to communicate new information comprehensibly and test the discoveries and hypotheses made by their authors).

Scientific Revolution , drastic change in scientific thought that took place during the 16th and 17th centuries. A new view of nature emerged during the Scientific Revolution, replacing the Greek view that had dominated science for almost 2,000 years. Science became an autonomous discipline , distinct from both philosophy and technology , and it came to be regarded as having utilitarian goals. By the end of this period, it may not be too much to say that science had replaced Christianity as the focal point of European civilization. Out of the ferment of the Renaissance and Reformation there arose a new view of science, bringing about the following transformations: the reeducation of common sense in favour of abstract reasoning; the substitution of a quantitative for a qualitative view of nature; the view of nature as a machine rather than as an organism; the development of an experimental, scientific method that sought definite answers to certain limited questions couched in the framework of specific theories; and the acceptance of new criteria for explanation, stressing the “how” rather than the “why” that had characterized the Aristotelian search for final causes.

The growing flood of information that resulted from the Scientific Revolution put heavy strains upon old institutions and practices. It was no longer sufficient to publish scientific results in an expensive book that few could buy; information had to be spread widely and rapidly. Natural philosophers had to be sure of their data, and to that end they required independent and critical confirmation of their discoveries. New means were created to accomplish these ends. Scientific societies sprang up, beginning in Italy in the early years of the 17th century and culminating in the two great national scientific societies that mark the zenith of the Scientific Revolution: the Royal Society of London for Improving Natural Knowledge , created by royal charter in 1662, and the Académie des Sciences of Paris, formed in 1666. In these societies and others like them all over the world, natural philosophers could gather to examine, discuss, and criticize new discoveries and old theories. To provide a firm basis for these discussions, societies began to publish scientific papers. The old practice of hiding new discoveries in private jargon, obscure language, or even anagrams gradually gave way to the ideal of universal comprehensibility. New canons of reporting were devised so that experiments and discoveries could be reproduced by others. This required new precision in language and a willingness to share experimental or observational methods. The failure of others to reproduce results cast serious doubts upon the original reports. Thus were created the tools for a massive assault on nature’s secrets.

The Scientific Revolution began in astronomy. Although there had been earlier discussions of the possibility of Earth’s motion, the Polish astronomer Nicolaus Copernicus was the first to propound a comprehensive heliocentric theory equal in scope and predictive capability to Ptolemy’s geocentric system . Motivated by the desire to satisfy Plato’s dictum, Copernicus was led to overthrow traditional astronomy because of its alleged violation of the principle of uniform circular motion and its lack of unity and harmony as a system of the world. Relying on virtually the same data as Ptolemy had possessed, Copernicus turned the world inside out, putting the Sun at the centre and setting Earth into motion around it. Copernicus’s theory , published in 1543, possessed a qualitative simplicity that Ptolemaic astronomy appeared to lack. To achieve comparable levels of quantitative precision, however, the new system became just as complex as the old. Perhaps the most revolutionary aspect of Copernican astronomy lay in Copernicus’s attitude toward the reality of his theory. In contrast to Platonic instrumentalism , Copernicus asserted that to be satisfactory astronomy must describe the real, physical system of the world.

The reception of Copernican astronomy amounted to victory by infiltration. By the time large-scale opposition to the theory had developed in the church and elsewhere, most of the best professional astronomers had found some aspect or other of the new system indispensable. Copernicus’s book De revolutionibus orbium coelestium libri VI (“Six Books Concerning the Revolutions of the Heavenly Orbs”), published in 1543, became a standard reference for advanced problems in astronomical research, particularly for its mathematical techniques. Thus, it was widely read by mathematical astronomers, in spite of its central cosmological hypothesis , which was widely ignored. In 1551 the German astronomer Erasmus Reinhold published the Tabulae prutenicae (“Prutenic Tables”), computed by Copernican methods. The tables were more accurate and more up-to-date than their 13th-century predecessor and became indispensable to both astronomers and astrologers.

During the 16th century the Danish astronomer Tycho Brahe , rejecting both the Ptolemaic and Copernican systems, was responsible for major changes in observation, unwittingly providing the data that ultimately decided the argument in favour of the new astronomy. Using larger, stabler, and better calibrated instruments, he observed regularly over extended periods, thereby obtaining a continuity of observations that were accurate for planets to within about one minute of arc—several times better than any previous observation. Several of Tycho’s observations contradicted Aristotle’s system: a nova that appeared in 1572 exhibited no parallax (meaning that it lay at a very great distance) and was thus not of the sublunary sphere and therefore contrary to the Aristotelian assertion of the immutability of the heavens; similarly, a succession of comets appeared to be moving freely through a region that was supposed to be filled with solid, crystalline spheres. Tycho devised his own world system —a modification of Heracleides’ —to avoid various undesirable implications of the Ptolemaic and Copernican systems.

At the beginning of the 17th century, the German astronomer Johannes Kepler placed the Copernican hypothesis on firm astronomical footing. Converted to the new astronomy as a student and deeply motivated by a neo- Pythagorean desire for finding the mathematical principles of order and harmony according to which God had constructed the world, Kepler spent his life looking for simple mathematical relationships that described planetary motions. His painstaking search for the real order of the universe forced him finally to abandon the Platonic ideal of uniform circular motion in his search for a physical basis for the motions of the heavens.

In 1609 Kepler announced two new planetary laws derived from Tycho’s data: (1) the planets travel around the Sun in elliptical orbits , one focus of the ellipse being occupied by the Sun; and (2) a planet moves in its orbit in such a manner that a line drawn from the planet to the Sun always sweeps out equal areas in equal times. With these two laws, Kepler abandoned uniform circular motion of the planets on their spheres, thus raising the fundamental physical question of what holds the planets in their orbits. He attempted to provide a physical basis for the planetary motions by means of a force analogous to the magnetic force , the qualitative properties of which had been recently described in England by William Gilbert in his influential treatise , De Magnete, Magneticisque Corporibus et de Magno Magnete Tellure (1600; “On the Magnet, Magnetic Bodies, and the Great Magnet of the Earth”). The impending marriage of astronomy and physics had been announced. In 1618 Kepler stated his third law, which was one of many laws concerned with the harmonies of the planetary motions: (3) the square of the period in which a planet orbits the Sun is proportional to the cube of its mean distance from the Sun.

A powerful blow was dealt to traditional cosmology by Galileo Galilei , who early in the 17th century used the telescope , a recent invention of Dutch lens grinders, to look toward the heavens. In 1610 Galileo announced observations that contradicted many traditional cosmological assumptions. He observed that the Moon is not a smooth, polished surface, as Aristotle had claimed, but that it is jagged and mountainous. Earthshine on the Moon revealed that Earth, like the other planets, shines by reflected light. Like Earth, Jupiter was observed to have satellites; hence, Earth had been demoted from its unique position. The phases of Venus proved that that planet orbits the Sun, not Earth.

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Introduction

The Scientific Revolution was one of the central concepts in the history of science during most of the twentieth century. Its central idea is that a unique break in intellectual history generated modern science – or science tout court . Historians and philosophers of science have long debated the exact geo-historical coordinates of such an event, including which disciplines were involved in it and which material and intellectual causes produced this cultural change. In general, historians of the Scientific Revolution have assumed that it must have taken place in early modern Europe during the two or more centuries that culminated in the works of figures such as Leonardo da Vinci, Nicolaus Copernicus, Galileo Galilei, and Isaac Newton. Intellectual historians such as Alexandre Koyré regarded the Scientific Revolution as a spiritual achievement – one that was both philosophical and theoretical – whereas historical materialists such as Boris Hessen and Edgar Zilsel sought the...

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Omodeo, P.D. (2020). Scientific Revolution, Ideologies of the. In: Jalobeanu, D., Wolfe, C. (eds) Encyclopedia of Early Modern Philosophy and the Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-20791-9_561-1

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The Incommensurability of Scientific Theories

The term ‘incommensurable’ means ‘to have no common measure’. The idea traces back to Euclid’s Elements , where it was applied to magnitudes. For example, there is no common measure between the sides and the diagonal of a square. Today, such incommensurable relations are represented by irrational numbers. The metaphorical application of the mathematical notion specifically to the relation between successive scientific theories became controversial in 1962 after it was popularised by two influential philosophers of science: Thomas Kuhn and Paul Feyerabend. They appeared to be challenging the rationality of science and so were often considered to be among “the worst enemies of science” (Theocharis and Psimopoulos 1987, 596; cf. Preston et al . 2000). Since 1962, the incommensurability of scientific theories has been a widely discussed, controversial idea that was instrumental in the historical turn in the philosophy of science and the establishment of the sociology of science as a professional discipline.

1. Introduction

2.1 the structure of scientific revolutions, 2.2 kuhn’s route to incommensurability, 2.3 kuhn’s subsequent development of incommensurability, 3.1 ‘explanation, reduction and empiricism’ (1962), 3.2 feyerabend’s route to incommensurability, 3.3 feyerabend’s later notions of incommensurability, 4. a comparison of kuhn and feyerabend on incommensurability, other internet resources, related entries.

In the influential The Structure of Scientific Revolutions (1962), Kuhn made the dramatic claim that history of science reveals proponents of competing paradigms failing to make complete contact with each other’s views, so that they are always talking at least slightly at cross-purposes. Kuhn characterized the collective reasons for these limits to communication as the incommensurability of pre- and post-revolutionary scientific traditions, claiming that the Newtonian paradigm is incommensurable with its Cartesian and Aristotelian predecessors in the history of physics, just as Lavoisier’s paradigm is incommensurable with that of Priestley’s in chemistry (Kuhn 1962, 147–150; cf. Caamaño 2009 and Hoyningen-Huene 2008). These competing paradigms lack a common measure because they use different concepts and methods to address different problems, limiting communication across the revolutionary divide. Kuhn initially used incommensurability predominately to challenge cumulative characterizations of scientific advance, according to which scientific progress is an improving approximation to the truth, and to challenge the idea that there are unchanging, neutral methodological standards for comparing theories throughout the development of the natural sciences. Like in evolution, the process does not change toward some fixed goal according to some fixed rules, methods or standards, but rather it changes away from the pressures exerted by anomalies on the reigning theory (Kuhn 1962, 170–173). The process of scientific change is eliminative and permissive rather than instructive. In the process of confronting anomalies, certain alternatives are excluded, but nature does not guide us to some uniquely correct theory.

Kuhn developed and refined his initial idea over the following decades, repeatedly emphasizing that incommensurability neither means nor implies incomparability; nor does it make science irrational (e.g. Kuhn 2000 [1970], 155ff.). He focused increasingly on conceptual incompatibility as manifest in the structural differences used to classify the kinds whose relations are stated in laws and theories, such as chemical elements and biological species (Kuhn 2000, see especially chs. 3, 4, 5, 10 & 11). He used incommensurability to attack the idea, prominent among logical positivists and logical empiricists, that comparing theories requires translating their consequences into a neutral observation language (cf. Hoyningen-Huene 1993, 213–214). In the late 1990s, he explicated incommensurability in terms of ineffability , emphasizing that it became possible for scientists to make and understand certain new statements only after a particular theory had been introduced (in the older vocabulary the new sentences are nonsensical), just as it only becomes possible for historians to understand certain older statements by setting aside current conceptions that otherwise cause distortions (Kuhn 2000 [1989], 58–59; 2000 [1993], 244). Such ‘ taxonomic incommensurability ’ results in translation failure between local subsets of inter-defined terms due to the cross-classification of objects into mutually exclusive taxonomies. This can be distinguished from ‘ methodological incommensurability ’, according to which there is no common measure between successive scientific theories, in the sense that theory comparison is sometimes a matter of weighing historically developing values, not following fixed, definitive rules (Sankey and Hoyningen-Huene 2001, vii-xv). This makes rational disagreement about theory comparison possible, as scientists may apply different values (such as scope, simplicity, fruitfulness, accuracy) in evaluating and comparing particular theories, so that theory choice is not unequivocally determined throughout the scientific community.

Paul Feyerabend initially used the term ‘incommensurable’ in “Explanation, Reduction and Empiricism” (1962). By calling two rival theories incommensurable, Feyerabend meant that they are ‘deductively disjoint’ due to meaning variance in the concepts used to state them. For example, Feyerabend claimed that the concepts represented by ‘temperature’ and ‘entropy’ in kinetic theory are incommensurable with those of phenomenological thermodynamics (1962, 78); and the Newtonian concepts represented by ‘mass’, ‘length’ and ‘time’ are incommensurable with their relativistic counterparts (1962, 80). By calling two rival theories deductively disjoint (or ‘incommensurable’), Feyerabend meant that one cannot be deduced from the other, nor can any predictions deduced from one enter formal logical relations with any predictions deduced from the other. Because the rival theories give different meanings to the same observation sentences when they are used to corroborate them by being deduced from them, the new theory cannot explain (formally by deduction) the successful predictions deduced from the established theory, and successful predictions deduced from one cannot logically contradict unsuccessful predictions deduced from the other potentially falsifying it (1962, 94, fn. 115).

Feyerabend developed a model to illustrate how there can be crucial experiments between incommensurable rivals despite the impossibility of establishing formal relations between them and any of their corresponding predictions. He illustrated his test-model with an example borrowed from David Bohm: the corroboration of the kinetic theory (atomism) by the confirmation of Einstein’s predictions of the stochastic character of Brownian motion (Oberheim 2024). Feyerabend repeatedly used the idea of incommensurability and this test-model to challenge a wide range of forms of conceptual conservatism for unjustifiably favoring entrenched views over potential improvements, and to support his methodological argument for theoretical pluralism as it became the lynchpin of his normative philosophy from ERE (1962) through Against Method (1993). Incommensurable alternatives to well-established views should always be welcome because they may be necessary for showing those views should be replaced.

The entry is organized around the 1962 popularizations of the concept of incommensurability by Kuhn and Feyerabend and the basic ideas that influenced their developments of this concept. First, Kuhn’s notion of incommensurability as it was initially developed is characterized, as is its cause and its purported consequences. That is followed by an examination of Kuhn’s route to the idea, and then his subsequent development after 1962. The sections on Feyerabend’s notion of incommensurability mirror the same basic structure. They are followed by a brief comparison of Kuhn and Feyerabend’s views on incommensurability, especially its relation to theory comparison.

2. Revolutionary paradigms: Thomas Kuhn on incommensurability

Kuhn’s notion of incommensurability in The Structure of Scientific Revolutions misleadingly appeared to imply that science was somehow irrational, and consequently, it faced many challenges and caused much confusion. This led to many clarifications, and eventually to a substantial redevelopment of a more precise and restricted version of it over the following decades. Kuhn initially used the term holistically to capture methodological, observational, and conceptual disparities between successive scientific paradigms that he had encountered in his historical investigations into the development of the natural sciences (Kuhn 1962, 148–150). Later, he refined the idea arguing that incommensurability is due to differences in the taxonomic structures of successive scientific theories and neighboring contemporaneous sub-disciplines. Kuhn’s developing notion of incommensurability has received much attention, and it continues to provoke plenty of controversy (cf. Bird 2007, Demir 2008, Moreno 2009, Psillos 2008, and Soler, Sankey and Hoyningen-Huene 2008).

In The Structure of Scientific Revolutions (1962), Thomas Kuhn used the term ‘incommensurable’ to characterize the holistic nature of the changes that take place in a scientific revolution. His investigations into the history of science revealed a phenomenon often now called ‘Kuhn loss’: Problems whose solution was vitally important to the older tradition may temporarily disappear, become obsolete, or even unscientific. On the other hand, problems that had not even existed, or whose solution had been considered trivial, may gain extraordinary significance in the new tradition. Kuhn concluded that proponents of incommensurable theories have different conceptions of their discipline and different views about what counts as good science; and that these differences arise because of changes in the list of problems that a theory must resolve and a corresponding change in the standards for the admissibility of proposed solutions (cf. Stillwaggon Swan and Bruce 2011). For example, Newton’s theory was initially widely rejected because it did not explain the attractive forces between matter, something required of any mechanics from the perspective of the proponents of Aristotle and Descartes’ theories (Kuhn 1962, 148). According to Kuhn, with the acceptance of Newton’s theory, this question was banished from science as illegitimate, only to re-emerge with the solution offered by general relativity. He concluded that scientific revolutions alter the very definition of science itself.

Changes in problems and standards come with corresponding conceptual changes, so that after a revolution, many (though not all) of the older concepts are still used, but in a slightly modified way. Such conceptual changes have both intentional and extensional aspects, which is to say that the same terms take on different meanings and are used to refer to different things when used by proponents of competing incommensurable theories. The changes in the intentional aspects of concepts result because the terms used to express a theory are inter-defined and their meanings depend on the theories to which they belong. For example, the meanings of the terms ‘temperature’, ‘mass’, ‘chemical element’, and ‘chemical compound’ depend on which theories are used to interpret them. Conceptual changes also result in the exclusion of some old elements of the extension of a concept, while new elements come to be subsumed by it so that the same term comes to refer to different things. For example, the term ‘Planet’ referred to the sun but not the earth in the Ptolemaic theory, whereas it refers to the earth and not the sun in the Copernican theory. Incommensurable theories use some of the same terms, but with different meanings, to refer to different sets of things. Two scientists who perceive the same situation differently, but nevertheless use the same vocabulary to describe it, speak from incommensurable viewpoints (Kuhn 1970, 201).

One of the most controversial claims to emerge from Kuhn’s assertions about the incommensurability of scientific theories is that the proponents of different paradigms work in different worlds (Kuhn 1962, 150; cf. Hoyningen-Huene 1990; 1993; 2021, 2022, 2023), but see also the metaphorical-psychological interpretation of world change in (Bird, 2012), pp. 869, 871). Drawing on experiments in the psychology of perception, Kuhn argued that the rigorous training required for admittance to a paradigm conditions scientist’s reactions, expectations and beliefs (Kuhn 1962, 128; 2000 [1989], 66–71), so that learning how to apply the concepts of a theory to solve exemplary problems determines scientists’ experiences. For example, where a proponent of the Newtonian theory sees a pendulum, an Aristotelian saw constrained free fall; where Priestley saw dephlogisticated air, Lavoisier saw oxygen; where Berthollet saw a compound that could vary in proportion, Proust saw only a physical mixture. Kuhn (and Feyerabend) used the analogy of a Gestalt switch to illustrate this point. In this way, one main source of the notion of incommensurability of scientific theories has been the development of Gestalt psychology.

According to Kuhn, these three interrelated aspects of incommensurability (changes in problems and standards that define a discipline, changes in the concepts used to state and solve those problems, and world change) jointly constrain the interpretation of scientific advance as cumulative. Scientific progress, Kuhn argued, is not simply the continual discovery of new facts duly explained. Instead, revolutions change what counts as the facts in the first place. When reigning theories are replaced by incommensurable challengers, the purported facts are re-described according to new and incompatible theoretical principles. The main goal of Kuhn’s Structure was to challenge the idea of scientific progress as cumulative, according to which what is corrected or discarded in the course of scientific advance is that which was never really scientific in the first place, and Kuhn used incommensurability as the basis of his challenge. Instead of understanding scientific progress as a process of change toward some fixed truth, Kuhn compared his suggestion to that of Darwin: scientific progress is like evolution in that its development should be understood without reference to a fixed, permanent goal (1962, 173).

2.2.1 Kuhn’s discovery of incommensurability

According to Kuhn, he discovered incommensurability as a graduate student in the mid to late 1940s while struggling with what appeared to be nonsensical passages in Aristotelian physics (Kuhn 2000 [1989], 59–60). He could not believe that someone as extraordinary as Aristotle could have written them. Eventually, patterns in the disconcerting passages began to emerge, and then all at once, the text made sense to him: a Gestalt switch that resulted when he changed the meanings of some of the central terms. He saw this process of meaning changing as a method of historical recovery. He realized that in his earlier encounters, he had been projecting contemporary meanings back into his historical sources (Whiggish history), and that he would need to peel them away to remove the distortion and understand the Aristotelian system in its own right (hermeneutic history). For instance, when he encountered the word “motion” in Aristotle (the standard translation of the Greek kinesis ), he was thinking in terms of the change of position of objects in space (as we do today). But to get more closely at Aristotle’s original usage, he had to expand the meaning of motion to cover a much broader range of phenomena that include various other sorts of change, such as growth and diminution, alternation, and generation and corruption, making the motion of an object in space (displacement or ‘locomotion’) just a special case of motion. Kuhn realized that these sorts of conceptual differences indicated breaks between different modes of thought, and he suspected that such breaks must be significant both for the nature of knowledge and for the sense in which the development of knowledge can be said to make progress. Having made this discovery, Kuhn changed his career plans, leaving theoretical physics to pursue this strange phenomenon. Some fifteen years later the term ‘incommensurable’ first appears in his classic The Structure of Scientific Revolutions (1962).

2.2.2 Conceptual replacement and theory-ladenness of observation: Ludwik Fleck

Of all the sources influencing Kuhn on incommensurability, at least one deserves special attention. In the foreword of The Structure of Scientific Revolutions , Kuhn acknowledged a deep debt to Ludwik Fleck, a bacteriologist who developed the first explicit sociology of science, anticipating many contemporary views about the social construction of knowledge. Around 1950, Kuhn was enticed by the potential relevance to his experience of incommensurability of Fleck’s paradoxical title: Entstehung und Entwicklung einer wissenschaftlichen Tatsache: Einführung in die Lehre von Denkstil und Denkkollektiv (1935) (Genesis and Development of a Scientific Fact , 1979). There and in other earlier works, Fleck had already used ‘inkommensurabel’ to describe different styles of thinking within the natural sciences as well as to discuss the ramifications of radical conceptual change in the history of science. For example, Fleck used the term ‘inkommensurabel’ to describe the differences between ‘medical thinking’ and ‘scientific thinking’. The former addresses irregular, temporally dynamic phenomena such as illness, while the latter addresses uniform phenomena (Fleck 1986 [1927], 44–45). Fleck also used the term ‘inkommensurabel’ to describe conceptual replacements in theoretical transitions within what he considered the most vital of the natural sciences, the medical sciences. For example, he claimed that an old concept of disease became incommensurable with a newer concept that was not a completely adequate substitute for it (Fleck 1979 [1935], 62). While Fleck’s program of comparative epistemology anticipates Kuhn’s ideas in many significant respects, it is also strikingly different in others (Harwood 1986; Oberheim 2006; Peine 2011). The most pervasive differences concerning incommensurability are that Fleck treats meaning and meaning change as a function of how concepts are received and developed by collectives, while for Kuhn it is individuals who develop and apply concepts that advance science. Moreover, for Fleck, meaning change is a gradual, continuous feature of scientific development, whereas Kuhn distinguishes normal scientific development that does not radically change meanings from revolutionary breaks that do.

Even so, Fleck had emphasized all three of the interrelated aspects of the shifts that Kuhn called scientific revolutions that result in ‘incommensurability’ (changes in problems and standards (1979 [1935], 75–76; 1979 [1936], 89), conceptual change (e.g. 1979 [1935]; 1979 [1936], 72, 83) and world change (e.g. 1986 [1936], 112). Fleck also argued that science does not approach the truth because successive thought-styles raise new problems and discard older forms of knowledge (Fleck 1986 [1936], 111–112; 1979 [1935], 19, 51, 137–139; cf. Harwood 1986, 177). Fleck emphasized that scientific terms acquire their meanings through their application within a particular theoretical context and that those meanings change when theories change in the course of advance, illustrating his point with the example of ‘chemical elements’ and ‘compounds’ repeated by Kuhn (Fleck 1979 [1935], 25, 39, 40, 53–54). Fleck emphasized the theory-ladenness of observation with explicit reference to Gestalt switches; stressing that a ‘thought-style’ determines not only the meanings of its concepts but also the perception of phenomena to be explained, illustrating his claims with examples from the history of anatomical representation (1979 [1935], 66; 1986 [1947]). Fleck (like Kuhn, Feyerabend, and Wittgenstein) acknowledged Wolfgang Köhler’s earlier work in the psychology of perception in this regard, see below (Oberheim 2006). Fleck concluded that scientific advance is not cumulative, that conceptual differences between members of different scientific communities cause communication difficulties between them (1979 [1936], 109), and later for historians trying to understand older ideas (1979 [1936], 83–85, 89). Fleck even emphasized that meaning change through scientific advance causes translation failure between theories, anticipating a central aspect of Kuhn’s later notion of taxonomic incommensurability (e.g. 1986 [1936], 83).

2.2.3 Gestalt psychology and organized perception

Another major source of Kuhn’s idea of the incommensurability of scientific theories is Gestalt psychology (Kuhn 1962, vi). Wolfgang Köhler had emphasized the active role of organization in perception and argued that in psychology one begins with Gestalten (organized, segregated wholes such as the objects of human perception or identifiable human behaviors) and then proceeds to discover their natural parts (and not vice versa, like in particle physics). In the opening sentences of the condensed English version of Köhler’s investigation of the relationship between the mental concepts of psychology and the material concepts of physics, Köhler wrote: “In order to orient itself in the company of natural sciences, psychology must discover connections wherever it can between its own phenomena and those of other disciplines. If this search fails, then psychology must recognize that its categories and those of natural science are incommensurable” (1938 [1920], 17).

2.2.4 The image of art and the image of science

In a preliminary draft, “The Structure of Scientific Revolutions, Chapter 1, What are Scientific Revolutions?” (dated 1958–1960, likely composed in late 1958) of the first chapter of his projected book, Kuhn initially used the idea of incommensurability to characterize stages of development in the arts in contrast to the traditional image of scientific progress as cumulative that he set out to challenge (see Pinto de Oliveira, 2017). Although this draft chapter was entirely rewritten as the introduction of Kuhn (1962), and was explicitly intended only to provoke exploratory discussion and not for publication, it strongly suggests that, at that time, Kuhn began to develop the idea of the incommensurability in science in reaction to the traditional (e.g. Sarton, Conant) contrast between development in the arts and cumulative progress in the sciences (see Pinto de Oliveira, 2017). In the draft, Kuhn announced his project as an attempt to reshape the image of science so as to make it closer to the image of art (see Pinto de Oliveira, 2017). He wanted to challenge the cumulative conception of scientific progress promoted by the old historiography of science, according to which “science appears to advance by accretion” and science is “an ever-growing edifice to which each scientist strives to add a few stones or a bit of mortar” (Kuhn 1958, 2, as cited in Pinto de Oliveira 2017, 748) in contrast to the image of art according to which “the transition between one stage of artistic development and the next is a transition between incommensurables” (Kuhn 1958, 3, as cited in Pinto de Oliveira 2017, 749).

A few pages later, Kuhn proceeds to apply the idea of incommensurability to science for the very first time, again while comparing scientific revolutions to the non-cumulative nature of progress in the arts: “Often a decision to embrace a new theory turns out to involve an implicit redefinition of the corresponding science. Old problems may be relegated to another science or may be declared entirely ‘unscientific’. Problems that, on the old theory, were non-existent or trivial may, with a new theory, become the very archetypes of significant scientific achievement. And, as the problems change, so, often, does the standard that distinguishes a real scientific solution from a mere metaphysical speculation, word game, or mathematical play. It follows that, to a significant extent, the science that emerges from a scientific revolution is not only incompatible, but often actually incommensurable, with that which has gone before. Only as this is realized, can we grasp the full sense in which scientific revolutions are like those in the arts” (Kuhn 1958, 17–18 as cited in Pinto de Oliveira 2017, 756). Kuhn concludes that “If we are to preserve any part of the metaphor which makes inventions and discoveries new bricks for the scientific edifice, and if we are simultaneously to give resistance and controversy an essential place in the development of science, then we may have to recognize that the addition of new bricks demands at least partial demolition of the existing structure, and that the new edifice erected to include the new brick is not just the old one plus, but a new building. We may, that is, be forced to recognize that new discoveries and new theories do not simply add to the stock of pre-existing scientific knowledge. They change it.” (Kuhn 1958, 7, as cited in Pinto de Oliveira 2017, 756).

Kuhn continued to struggle with, develop, and then refine his understanding of incommensurability until his death in 1996. Although his development of incommensurability went through several stages (cf. Hoyningen-Huene 1993, 206–222), he claimed to have made a “series of significant breakthroughs” beginning in 1987 (Kuhn 2000 [1993], 228). They are described in several essays and published lectures that were collected in (Kuhn 2000, cf. chs. 3, 4, 5, 10 & 11), and an unfinished book entitled The Plurality of Worlds: An Evolutionary Theory of Scientific Development . Kuhn only wrote six out of nine planned chapters of the book that was published, together with other writings (Mladenovic, 2022). The relationships among Kuhn’s posthumously published writing that partly overlap have been analyzed in (Melogno, 2023). The nature of these developments is controversial. Some commentators claim that Kuhn’s incommensurability thesis underwent a ‘major transformation’ (Sankey 1993), while others (including Kuhn himself) see only a more specific characterization of the original core insight (Hoyningen-Huene 1993, 212; Kuhn 2000, [1983], 33ff.; Chen 1997). Kuhn’s original holistic characterization of incommensurability is now distinguished into two separate theses. ‘Taxonomic incommensurability’ involves conceptual change in contrast to ‘methodological incommensurability’, which involves the epistemic values used to evaluate theories (Sankey 1991; Sankey and Hoyningen-Huene 2001; see Section 2.3.2 below).

2.3.1 Taxonomic incommensurability

To help explicate incommensurability in terms of taxonomic classification, Kuhn developed the no-overlap principle . The no-overlap principle precludes cross-classification of objects into different kinds within a theory’s taxonomy. According to the no-overlap principle, no two kind terms may overlap in their referents unless they are related as species to genus. For example, there are no dogs that are also cats; no gold that is also silver, and that is what makes the terms ‘dogs’, ‘cats’, ‘silver’, and ‘gold’ kind terms (Kuhn 2000 [1991], 92). Such kind terms are used to state laws and theories and must be learned together through experience (2000 [1993], 230; cf. Barker et al. 2003, 214 ff.). There are two possibilities. Most kind terms must be learned as members of one or another contrast set. For example, to learn the term ‘liquid’, one must also master the terms ‘solid’ and ‘gas’. Other types of kind terms are not learned through contrast sets, but together with closely related terms through their joint application to situations that exemplify natural laws. For example, the term ‘force’ must be learned together with terms like ‘mass’ and ‘weight’ through an application of Hooke’s law and either Newton’s three laws of motion or else the first and third laws together with the law of gravity (2000 [1993], 231). According to Kuhn, scientific revolutions change the structural relations between pre-existing kind terms, breaking the no-overlap principle (2000 [1991], 92–96]. This is to say that theories separated by a revolution cross-classify the same things into mutually exclusive sets of kinds. A kind from one taxonomy is mutually exclusive with another if it cannot simply be introduced into it because the objects to which it refers would be subject to different sets of natural laws. This would result in conflicting expectations about the same objects, loss of logical relations between statements made with those concepts, and ultimately incoherence and miscommunication (Kuhn 2000 [1993], 232, 238). For example, Ptolemy’s theory classifies the sun as a planet, where planets orbit the earth, while Copernicus’ theory classifies the sun as a star, where planets orbit stars like the sun. A correct statement according to Copernican theory, such as “Planets orbit the sun” is incoherent in Ptolemaic vocabulary (2000 [1991], 94). It could not even have been made without abandoning the Ptolemaic concepts and developing new ones to replace (and not supplement) them.

Furthermore, Kuhn (in a move toward Feyerabend’s view) later claims that the same types of difficulties in communication that arise due to incommensurability between members of different scientific communities separated by the passage of time also occur between members of different contemporaneous sub-disciplines that result from scientific revolutions (Kuhn 2000 [1993], 238). This represents a significant change to his original phase-model of scientific advance, and a corresponding shift in his application of the notion of incommensurability. Kuhn no longer represents scientific advance as a linear progression from pre-normal science to normal science, through crisis to revolution that results in a new phase of normal science; and incommensurability is no longer restricted just to diachronic episodes of scientific advance in which two theories are separated by a revolution. Instead, scientific revolutions are compared to the process of speciation in biology, in that disciplines branch into sub-disciplines that resemble a phylogenetic tree in which contemporaneous sub-disciplines that result from scientific revolutions can also be incommensurable. This incommensurability derives from different training required to master the incompatible kind terms used to state their laws and theories. These shared kind terms cross-classify the same set of objects into different sets of kinds, resulting in mutually exclusive lexical taxonomies that break the no-overlap principle. Moreover, now not only are both processes (scientific progress and biological evolution) similar in that they are not fixed in advance by some set goal (i.e. truth), but driven from behind (i.e. away from anomalies that play an analogous role to selection pressure), but also the function of incommensurability between scientific theories is presented as analogous to the isolating mechanisms required for speciation (Kuhn 2000 [1991], 94–99).

Kuhn compared the function of lexical taxonomies to Kant’s a priori when taken in a relativized sense. Each lexicon makes a corresponding form of life possible within which the truth or falsity of propositions may be both claimed and rationally justified. For example, with the Aristotelian lexicon, one can speak of the truth or falsity of Aristotelian assertions, but these truth values have no bearing on the truth of apparently similar assertions made with the Newtonian lexicon (Kuhn 2000 [1993], 244). A lexicon is thus constitutive of the objects of knowledge (Kuhn 2000 [1993], 245); and consequently, Kuhn rejected characterizations of scientific progress according to which science zeros in on the truth: “ no shared metric is available to compare our assertions … and thus to provide a basis for a claim that our (or, for that matter, his) are closer to the truth” (2000 [1993], 244). Instead, the logical status of a lexical structure, like that of word meanings in general, is that of convention, and the justification of a lexicon or of lexical change can only be pragmatic (2000 [1993], 244). Kuhn thus reaffirmed his earlier claim that the notion of a match or correspondence between the ontology of a theory and its real counterpart in nature is illusive in principle (1970, 206; 2000 [1993], 244). The implications that incommensurability has for scientific realism have been widely discussed and continue to be controversial (cf. Oberheim and Hoyningen-Huene 1997; Devitt 2001; Sankey 2009; Oberheim 2024).

A lexicon is not only prerequisite to making meaningful statements, it also sets limits on what can be meaningfully said within the community of speakers that share it: “There is, for example, no way, even in an enriched Newtonian vocabulary, to convey the Aristotelian propositions regularly misconstrued as asserting the proportionality of force and motion or the impossibility of a void. Using our conceptual lexicon, these Aristotelian propositions cannot be expressed — they are simply ineffable — and we are barred by the no-overlap principle from access to the concepts required to express them” (Kuhn 2000 [1993], 244; cf. 2000 [1989], 76). In this way, Kuhn’s later notion of the incommensurability of scientific theories is based on effability . The structure of the lexicon shared by a particular community determines how the world can be described by its members, as well as how they will misunderstand the history of their own discipline; that is, unless they learn to understand older terms according to the structure of the older lexicon. Where Kuhn had earlier likened the process by which historians come to understand antiquated science as a special type of translation, he retracted these claims, insisting that the process is one of language learning, not translation (2000 [1993], 238, 244). Kuhn often claimed that incommensurable theories are untranslatable (e.g. Kuhn 2000 [1991], 94). However, he also emphasized that translation is neither needed in the comparison of incommensurable theories, nor in the hermeneutic historical method necessary to understand antiquated sciences (Kuhn 2000 [1993], 237, 238, 244). To overcome the barriers posed by incommensurability to understanding antiquated sciences, and to understanding the special technical vocabulary used by contemporaneous, phylogenetically related sub-disciplines, it is neither necessary nor possible to translate between them. Rather, one must become bilingual , learning to use (and keep separate) the incongruently structured lexical taxonomies underwriting different laws and theories.

2.3.2 Methodological incommensurability

As Kuhn refined his notion of incommensurability as a special type of conceptual incompatibility, some commentators began to distinguish it from ‘methodological incommensurability’. Methodological incommensurability is the idea that there are no shared, objective standards of scientific theory appraisal, so that there are no external or neutral standards that univocally determine the comparative evaluation of competing theories (Sankey and Hoyningen-Huene 2001, xiii). This idea has also been recently discussed in detail under the rubric “Kuhn-underdetermination” (Carrier 2008, 278). The basic idea was developed out of Kuhn and Feyerabend’s rejections of the traditional view that a distinguishing feature of science is a uniform, invariant scientific method, that remains fixed throughout its development (Kuhn 1962, 94, 103; Feyerabend 1975, 23–32; cf. Farrell 2003). Feyerabend famously argued that every proposed methodological rule has been fruitfully violated at some point in the course of scientific advance, and that only by breaking such rules could scientists have made the progressive steps for which they are praised (1975). He concluded that the idea of a fixed, historically invariant scientific method is a myth. There are no universally applicable methodological rules. The only methodological rule that is universally applicable is ‘anything goes’, which buys its universality at the cost of being completely empty (1970a, 105). Kuhn challenged the traditional view of scientific method as a set of rules, claiming that the standards of theory appraisal, such as simplicity, accuracy, consistency, scope, and fruitfulness (1977, 322), depend on and vary with the currently dominant paradigm. He is often cited for having pointed out that as in political revolutions, so in choice of paradigm, there is no standard higher than the assent of the relevant community (1962, 94), and as having argued that there is “no neutral algorithm for theory choice, no systematic decision procedure which, properly applied, must lead each individual in the group to the same decision” (1970, 200). Kuhn developed the idea that such epistemic standards do not function as rules that determine rational theory choice, but as values that merely guide it (1977, 331). Different scientists apply these values differently, and they may even pull in different directions, so that there may be rational disagreement between scientists from incommensurable paradigms, who support different theories due to their weighing the same values differently.

3. Combating conceptual conservatism: Paul Feyerabend on incommensurability

In Feyerabend’s philosophy, incommensurability is a specific form of “conceptual disparity” that results in incompatible interpretations of reality (1970b, 222). For there to be incommensurability: “The situation must be rigged in such a way that the conditions of concept formation in one theory forbid the formation of the basic concepts of the other” (1970b, 222; 1978, 68; and 1975, 269), so that the new theory entails that “all the concepts of the preceding theory have zero extension ” because the new theory introduces “rules that change the system of classes itself” (1965c, 268). Incommensurable theories are incompatible both conceptually and ontologically. They use incompatible sets of concepts to state mutually exclusive accounts of reality. They are conceptually incompatible because of meaning variance in the terms used to state the rival theories. They are ontologically incompatible because according to the new theory, the general descriptive terms used to state the established view do not in fact refer to real kinds of things; therefore, if one is true, then the other cannot be. According to Feyerabend, two theories are incommensurable because the meanings of the terms used to state them are determined by rival theoretical principles that govern their use, and these principles imply incompatible explanations of reality (1962, 58). Or put another way, two theories are incommensurable: “When the meaning of their main descriptive terms depend on mutually inconsistent [ontological] principles” (1965c, 227; cf. 1975, 269–270, 276), so that “a theory is incommensurable with another if [their] ontological consequences are incompatible” (1981a, xi).

With respect to normative methodology (Popper’s logic of scientific inquiry), the main consequences of incommensurability follow from the fact that incommensurable theories are deductively disjoint . Because the terms used to state the theories have different meanings, the main concepts of one can neither be defined based on the primitive descriptive terms of the other, nor formally related to them via correct empirical statements deduced from them (1962, 74, 90), so that for Feyerabend, incommensurability just means “deductive disjointedness, and nothing else” (1977, 365). By calling rival theories deductively disjoint or “incommensurable”, Feyerabend is claiming that in scientific revolutions, the established theory cannot be deduced from the new theory, nor can predictions deduced from the established theory enter formal relations with the new theory or any predictions deduced from it. Put more directly, if two theories are incommensurable, then one theory cannot be deduced from the other, nor can any of the predictions deduced from one theory be formally consistent or inconsistent with any predictions deduced from the other, or as Feyerabend put it, “incommensurable theories may not possess any comparable consequences, observational or otherwise” (1962, 94). Feyerabend often emphasizes that “this does not mean that a person may not, on different occasions, use concepts which belong to different and incommensurable frameworks. The only thing that is forbidden for him is the use of both kinds of concepts in the same argument; for example, he may not use the one kind of concept in his observation language and the other kind in his theoretical language” (1962, 83).

To explain incommensurability, Feyerabend develops what he took to be Wittgenstein’s views on meaning, specifically his nominalism and constructivism, with what he called a contextual theory of meaning , according to which a term does not have meaning independent of its use in a specific context, and its meaning is determined by the theory with which it is interpreted. This has the peculiar result, according to Feyerabend, that due to meaning variance in the terms used state rival theories, one sentence will covertly make two incompatible statements, when it is deduced from rival incommensurable theories and used to test them. Similarly, when two sentences that prima faci a directly logically contradict each other (“The ball fell down”, “The ball did not fall down”) are deduced from incommensurable rival theories, even though they may look like they formally contradict each other, they cannot because of meaning variance in the terms from which they were deduced. Feyerabend argues that for predictions to count as evidence for or against a theory, they must be deduced from that theory, and therefore, the same experimental results must be given incompatible interpretations that can have no formal relations when they are when they are used to test incommensurable rivals. In Feyerabend’s example, the sentence ‘The ball fell down’ will mean ‘The ball was pushed down by its impetus toward its natural place’, or it will mean ‘it was pulled by gravity toward the Earth’s center of mass’, depending on whether an Aristotelian or Newtonian theory is used to interpret it (1962, 56, citing Clagett 1959). Similarly, the terms ‘mass’ and ‘space’ mean something different in classical mechanics and relativity theory, which imply incompatible accounts of reality. If one of these theories is true, then the other cannot be. Either objects have an absolute mass and move in space that is inert, or objects have a rest mass and a relative mass and move in space that can bend and stretch. Because the meanings of the terms used to state the rival theories vary, classical mechanics cannot be deduced from relativity theory; and predictions deduced from classical mechanics can neither be logically consistent with (nor can they logically contradict) any predictions deduced from relativity theory. For this reason, according to Feyerabend, relativity theory cannot explain the successful predictions deduced from Newton’s theory, nor can predictions deduced from relativity theory falsify Newton’s theory by logically contradicting predictions deduced from it (1962, 28–31, 93–95).

Feyerabend’s landmark essay, “Explanation, Reduction and Empiricism” (1962), is an attempt to synthesize the best aspects of Popper and Wittgenstein’s views, while criticizing the worst aspects of each (Oberheim 2024). Feyerabend tries to analyze a problem with explanation (1962, 92, fn. 13) by developing the idea of incommensurability to criticize three views interpreted as normative methodologies, or accounts of the logic of scientific justification in the Popperian sense. Hempel’s account of explanation , Nagel’s account of reductionism , and Popper’s account of empiricism (also known as ‘falsificationism’); hence, the three-word title. Feyerabend argues that none of these three accounts can take comparing rival incommensurable theories empirically into account, and so they all dogmatically stifle the scientific progress that they should promote. Then, he generalizes his argument: Due to meaning variance that results from scientific revolutions, a formal account of explanation cannot be given (1962, 95). Put simply, today’s best theories cannot explain antiquated facts, because those facts cannot be deduced from them. Therefore, any methodology that implies that to be acceptable as a replacement for an established view, a new theory should have to explain the successful predictions deduced from it is antihumanitarian because it would stifle the progress it should promote.

According to Feyerabend, Hempel’s account of explanation implies that a statement is explained by an explanation by being deduced from it and that one explanation should replace another if it explains everything the existing theory explains plus more. According to Feyerabend, this is not possible whenever the rival explanations are incommensurable (‘deductively disjoint’) due to meaning variance in the terms used to state the explanations. If new proposed explanations should have to explain (by deduction) everything the established explanations explain (by deduction) to justify replacing the established explanation with the new proposal, then revolutionary scientific advances that result in meaning variance would never be justifiable. For this reason, Hempel’s account of explanation interpreted as a normative methodology has antihumanitarian consequences because it stifles the progress it should promote.

According to Feyerabend, Nagel’s account of reduction implies that the new theory should explain the established theory (or some form of it) by being shown to be deducible from it (as a limiting case), or in other words, the new theory explains (be deduction) the established theory in an explanation by ‘reduction’. According to Feyerabend, this is not possible if the rival theories are incommensurable. If new theories should have to explain established theories by showing that they (or some version of them) can be deduced from the new theory (or some version of it), then revolutionary scientific advances would never be justifiable. Moreover, as Popper has shown, according to Feyerabend, if the existing theory were a deductive consequence of the new theory, then the new theory could not predict – by deduction – a statement that falsifies the existing theory. Thus, Nagel’s account of reduction interpreted as a normative methodology also has antihumanitarian consequences because it stifles the progress it should promote.

According to Feyerabend, Popper’s account of empiricism implies that the new theory should falsify the established theory by meeting two conditions. First, it should predict (by deduction) all the statements the existing theory successfully predicted (by deduction) so that the evidence for the existing theory becomes evidence for the new theory and is explained by it (assuming that the new theory is true). Second, the new theory should correctly predict a statement that formally contradicts a statement deduced from the established view (1962, 91–93). According to Feyerabend, due to meaning variance in the terms used to state incommensurable rival theories, neither of these conditions can be met. The new theory cannot explain (by deduction) the predictions that were successfully deduced from the existing theory because of meaning variance (1962, 94), nor can a successful prediction deduced from the new theory falsify the existing theory by formally contradicting an unsuccessful prediction deduced from the existing theory (1962, 94, fn. 115). Feyerabend concludes that Popper’s methodology:

can well deal with all the problems that arise when T and T ′ are commensurable, but inconsistent inside D ′. It does not seem to me that it can deal with the case where T ′ and T are incommensurable. (1962, 93)

According to Feyerabend, by inadvertently implying meaning invariance in the terms used to test rival theories, which would be required to establish formal relations between them, Popper’s empiricism is much closer to the dogmatic school philosophies, such as Platonism and Cartesianism, from which it tries to distance itself (1962, 30–31). Moreover, the reason traditional philosophical problems such as the mind-body problem, the problem of the reality of the external world, and the problem of other minds perpetually persist is that the disputants resist the kind of meaning change necessary for their dissolution (1962, 31, 90). Similarly, Wittgenstein’s genuinely philosophical (pseudo-)problems (not genuine philosophical problems) perpetually re-occur, because antiquated incommensurable theoretical principles continue to haunt contemporary everyday language use. This happens because we continue to use the same terms to mean radically different things based on incompatible ontological principles after scientific revolutions. Throughout the 1960s, Feyerabend’s papers adamantly argued that everyday language should be perpetually revised and corrected to reflect the ontological implications of our current best theories (Feyerabend 1962; 1964; 1969).

By calling two theories incommensurable, Feyerabend did not mean to imply that they were not empirically comparable or comparatively untestable. For Feyerabend, falsifiability is not synonymous with testability. Feyerabend developed an alternative test model for empirically comparing incommensurable rivals, which he illustrated with the example of Einstein’s prediction of the stochastic character of Brownian motion as a “crucial experiment” between two incommensurable rivals: the kinetic theory (and atomism) and classical phenomenological thermodynamics (and energeticism) (1962, 66). In Feyerabend’s test model, in contrast to falsificationism, the new theory is better corroborated than the existing theory because it predicts a novel phenomenon that cannot be explained by the existing theory. Moreover, the existing theory, by itself, could never even have discovered the fact that the phenomenon in question refutes it because the existing theory implies incorrect basic postulates that are incompatible with the basic postulates needed to explain the phenomenon and thereby prove that it refutes the existing theory. In this way, the new theory undermines its rival’s ontology without falsifying it by logically contradicting predictions deduced from it. Put more directly, in contrast to Popper’s conjectures and refutations, Feyerabend’s theoretical pluralism is based on conjectures and novel corroborations. It follows from Feyerabend’s view that universal framework theories are never formally falsified, because they can always be protected from direct refutations by ad hoc maneuvers (a lesson he had learned firsthand from his Ehrenhaft experience in the late 1940s), and they cannot be indirectly refuted by falsification due to meaning invariance (Oberheim 2024). Through to Against Method (1993), Feyerabend repeatedly used this test model to support a methodological argument for theoretical pluralism. Incommensurable proposals should always be welcome because they can increase the testability of established views. For example, without a new incommensurable theory that correctly predicts its stochastic character, Brownian motion could never have dethroned classical phenomenological thermodynamics by undermining its ontology. Feyerabend argues that this implies a contrastive account of a theory’s empirical content (in contrast to Popper’s deductive account of empirical content). Incommensurable alternatives together with the facts they can explain are part of each other’s empirical content in contrast to each other, as part of what they rule out (1962, 67; 1993, 27–28). For Feyerabend, in scientific revolutions, established theories and the concepts used to state them are not corrected and absorbed , and thereby legitimized by new theories; rather, they are rejected and replaced by better corroborated alternatives, so that: “Knowledge so conceived is not a process that converges toward an ideal view; it is an ever-increasing ocean of alternatives, each of them forcing the others into greater articulation, all of them contributing, via this process of competition, to the development of our mental faculties” (1965c, 224–225; cf. 1963).

Although Feyerabend first used the term ‘incommensurable’ to describe deductively disjoint scientific theories in 1962, he had been developing ideas about conceptual change for more than a decade. According to Feyerabend, he initially discussed these ideas with the Kraft Circle from 1949–1951, while working toward his doctoral thesis on protocol statements (Feyerabend 1951; 1958). In 1952, Feyerabend presented his notion of incommensurability to Popper’s seminar at the London School of Economics and also in Elizabeth Anscombe’s home in Oxford to Anscombe and other Wittgensteinians, including Peter Geach, H.L.A.Hart and Georg Henrik von Wright (1995, 92). In an “An Attempt at a Realistic Interpretation of Experience” (which a condensed version of his 1951 Ph.D. thesis), Feyerabend argued for “thesis I: the interpretation of an observation-language is determined by the theories which we use to explain what we observe, and it changes as soon as those theories change” (Feyerabend 1958a, 163; Feyerabend 1993, 211). For example, according to Feyerabend, the correct meaning of the term ‘temperature’ should not be determined by how it feels phenomenologically or by its everyday use, but by the principles of statistical thermodynamics according to which it is caused by molecular motion. Feyerabend argued that as older theories are replaced, the meanings of the observational terms used to test those theories change. This is an early version of his idea that conceptually incompatible theories are incommensurable due to meaning differences. In 1958, Feyerabend challenged an implicit conceptual conservatism in logical positivism with his early notion of incommensurability, criticizing the assumptions that theoretical terms derive their meaning solely through their connection with experience and that experience is a stable foundation on which theoretical meaning can be unequivocally based. Instead of such a bottom-up version of the relation of experience and theoretical knowledge, according to which experience determines the meanings of our theoretical terms, Feyerabend argued for a top-down version, according to which our best theories determine the meanings that we attach to our experiences. According to Feyerabend, experience cannot be taken for granted as a neutral basis for comparing theories, because what we experience depends on the theories that we bring to it.

Karl Popper had quickly become Feyerabend’s mentor after they met in 1948, and there has been much controversy concerning Feyerabend’s evolving relationship to Popper (cf. Collodel 2016), especially given its tumultuous trajectory, and Feyerabend’s break with the Popperian school in 1967 (Oberheim 2024). Many factors have complicated these controversies, including the revisions Feyerabend made concerning his debts to Popper in the reprints of his original papers (see Preston 1997; Oberheim 2006; Collodel 2016), informal accusations of plagiarism by Popper and Popperians (Collodel 2016), and Feyerabend’s subsequent increasingly vocal denials of his debts to Popper as he tried to distance himself from Popper and his methodology (Oberheim 2006, ch. 3.4). Many (including Popper) have interpreted Feyerabend’s conception of incommensurability as a rather misguided extension of falsificationism and/or Popper’s earlier use of ‘inkommensurabilität’ (Bschir 2015; Collodel 2016; Gattei and Agassi 2016). However, in 1962 Feyerabend explicitly tried to criticize Popper’s methodology as a dogmatic school philosophy with a limited validity (limited to testing commensurable theories empirically), not to extend it (Oberheim 2024). This marks the point that Feyerabend and Popper begin to part ways concerning their views on scientific progress and truth (Tambolo 2017). Moreover, Feyerabend’s 1962 criticism of Popper’s methodology eventually resulted in Feyerabend announcing his break from the Popperian school in late November 1967, as can clearly be seen in his correspondence with Imre Lakatos and John Watkins (Oberheim 2024).

Feyerabend’s route to the idea of incommensurability was influenced by several prominent individuals, who had been discussing a wide range of related topics. An investigation of the source of these ideas reveals some of the founding fathers of the notion of incommensurability in the contemporary history and philosophy of science (see Oberheim 2006, ch. 5).

3.2.1 Progress through meaning change: Pierre Duhem

Feyerabend drew heavily from Duhem’s The Aim and Structure of Physical Theory (1954 [1906]) in his development of the notion of incommensurability of scientific theories. Many of the main points Feyerabend emphasized by calling scientific theories incommensurable had been developed already by Duhem, who had argued that logic is insufficient for determining the outcome of theoretical disputes in the natural sciences, and who documented the difficulties historians have in understanding the development of the natural sciences due to meaning change. Duhem also already highlighted the communication difficulties between proponents of competing scientific theories because of these differences in meaning. For example, Duhem had claimed that what a physicist states as the result of an experiment is not simply the recital of some observed facts. Rather, it is the interpretation of these facts on the basis of the theories the scientist regards as true (1954 [1906], 159). It follows, according to Duhem, that in order to understand the meanings that scientists ascribe to their own statements, it is necessary to understand the theories that they use in order to interpret what they observe. Thus, Duhem had stated an early version of Feyerabend’s incommensurability thesis. Moreover, Duhem explicitly limited his discussion to non-instantial, physical theories, as opposed to mere experimental laws. This is very similar to the criteria that marks the most significant difference between Kuhn and Feyerabend’s development of the idea of incommensurability (see Section 4), and that also delimits Einstein’s use of ‘incommensurable’ while discussing the problems of theory comparison (see Section 3.2.3).

After explaining that the meaning of a term depends on the theory to which it belongs, and that a consequence of theoretical advance is meaning change, Duhem continued: “If the theories admitted by this physicist are those we accept, and if we agree to follow the same rules in the interpretation of the same phenomena, we speak the same language and can understand each other. But that is not always the case. It is not so when we discuss the experiments of a physicist who does not belong to our school; and it is especially not so when we discuss the experiments of a physicist separated from us by fifty years, a century, or two centuries” (1954 [1906], 159). Duhem continued: “How many scientific discussions there are in which each of the contenders claims to have crushed his adversary under the overwhelming testimony of the facts! … How many propositions are regarded as monstrous errors in the writings of those who have preceded us! We should perhaps commemorate them as great truths if we really wished to enquire into the theories which gave their propositions their true meaning” (Duhem 1954 [1906], 160–161). These passages make the same basic points that both Feyerabend and Kuhn made with their claims about incommensurability of scientific theories: Because older ideas are misunderstood, as a result of taking them out of their theoretical context, proponents of incommensurable scientific theories misunderstand each other, both claiming to have the facts on their side. Kuhn and Feyerabend both claimed that in such a situation, even empirical arguments can become circular (Feyerabend 1965b, 152; Kuhn 1962, 94).

3.2.2 The square root of 2 and complementarity: Niels Bohr

In his autobiography, Feyerabend acknowledged Niels Bohr’s direct influence on the development of his notion of incommensurability in the 1950s. Feyerabend recalled a conversation in which Bohr had talked about the discovery that the square root of two cannot be an integer or a fraction. According to Feyerabend, Bohr presented the event as having led to the extension of a concept of number that retained some properties of integers and fractions, but changed others; and claimed that the transition from classical to quantum mechanics was carried out in accordance with precisely this principle (1995, 78). Feyerabend also used the notion of incommensurability to argue that Bohr’s complementarity thesis is an example of an unjustified conceptual conservatism, taking issue with Bohr’s contention that all quantum mechanical evidence will always necessarily be expressed in classical terms (Feyerabend 1958b; cf. 1962). He presented Bohr’s defense of the principle of complementarity as based on the conviction that every experience must necessarily make its appearance within the frame of our customary points of view, which is currently that of classical physics. However, according to Feyerabend, even though classical concepts have been successful in the past, and even though at the moment it may be difficult, or even impossible, for us to imagine how to replace them, it does not follow that the classical framework could not one day be superseded by an incommensurable rival. Consequently, it does not follow that all our future microscopic theories will have to take the notion of complementarity as fundamental. Instead, according to Feyerabend, a theory may be found whose conceptual apparatus, when applied to the domain of validity of classical physics, would be just as comprehensive and useful as the classical apparatus, without coinciding with it. He claimed that such a situation is by no means uncommon, and he used the transition from Newtonian to relativistic physics to bolster his point. According to Feyerabend, while the concepts of relativity theory are sufficiently rich to state all of the facts captured by Newtonian physics, the two sets of concepts are “completely different” and bear “no logical relations” to each other (1958b, 83; 1961, 388; 1962, 88–89). On Feyerabend’s fallibilist view of empirical knowledge, no element of our knowledge can be held to be necessary or absolutely certain. In our search for satisfactory explanations, we are at liberty to change any parts of our existing knowledge, however fundamental they may seem, including the concepts of classical physics.

3.2.3 ‘Kant on wheels’ and universal theories: Albert Einstein

Albert Einstein used the term ‘incommensurable’ to apply specifically to difficulties selecting and evaluating scientific theories before Kuhn and Feyerabend, and there are very strong reasons to believe that Feyerabend’s use of the term “incommensurable” was directly inspired by Einstein’s use of the term (Oberheim 2016, Oberheim 2024). In his ‘Autobiographical notes’ (1949), Einstein attempted to explain that assessing the relative merits of universal physical theories involves making difficult judgments about their ‘naturalness’ that requires making judgments based on the reciprocal weighing of incommensurable qualities: “The second point of view is not concerned with the relation to the material observation but with the premises of the theory itself, with what may briefly but vaguely be characterized as the ‘naturalness’ or ‘logical simplicity’ of the premises (of the basic concepts and of the relations between these which are taken as a basis). This point of view, an exact formulation of which meets with great difficulties, has played an important role in the selection and evaluation of theories since time immemorial. The problem here is not simply one of a kind of enumeration of the logically independent premises (if anything like this were at all unequivocally possible), but that of a kind of reciprocal weighing of incommensurable qualities” (1949a, 23).

There are strong reasons for believing that these admittedly cryptic remarks directly inspired Feyerabend’s use and development of the idea of incommensurability. In his 1962 paper, Feyerabend cites from Bohr’s paper, which is in same edited volume as Einstein’s autobiographical notes (Schilpp 1949), and David Bohm had brought the Brownian motion example to Feyerabend’s attention, which is discussed by Einstein in those autobiographical notes (Oberheim 2024). Feyerabend’s main example illustrating that and how incommensurable theories can be compared based on a ‘crucial experiment’ was Einstein’s quantitative prediction, and Perrin’s subsequent confirmation, of Brownian motion. Feyerabend argued that although Brownian motion was already a well-known phenomenon, it became evidence for statistical thermodynamics and against classical thermodynamics only after kinetic theory was used to explain it. The crucial experiment between these two rival theories was based on theory-laden observations of Brownian motion that corroborated statistical thermodynamics, but because they are theory-laden, they cannot be stated in a neutral observation language.

There are striking similarities between Feyerabend and Einstein’s uses of the term. Both make a distinction between universal theories and lower-level theories that do not apply to the totality of all physical appearances and then use this distinction to limit the application of incommensurability in the same way that is to such universal theories (cf. Feyerabend 1962, 28 and Einstein 1949a, 23), and they both apply “incommensurable” directly to differences in the basic concepts used to state the theories. Furthermore, Einstein’s theoretical attitude is a form of dynamic Kantian realism, or “Kantian-on-wheels” – to use Peter Lipton’s apt expression (Lipton 2001) – very much like that of Feyerabend and Kuhn’s (Oberheim 2016). According to Einstein, his theoretical attitude “is distinct from that of Kant only by the fact that we do not conceive of the ‘categories’ as unalterable (conditioned by the nature of the understanding) but as (in the logical sense) free conventions. They appear to be a priori only insofar as thinking without the positing of categories and of concepts in general would be as impossible as is breathing in a vacuum” (Einstein 1949b, 374). This is the same basic perspective that both Kuhn and Feyerabend delineated when they developed their ideas of incommensurability. For example, Kuhn says, “I go around explaining my own position saying I am a Kantian with moveable categories” (Kuhn 2000 [1995], 264), an idea developed in detail by Hoyningen-Huene (1993). For his part, Feyerabend adopted such a ‘Kant-on-wheels’ approach in the introduction of ‘Explanation, Reduction and Empiricism’ (1962) to pursue the question: If universal theories determine all of our experiences of the world, how can experience still be used to test such theories? Feyerabend also defended his view that there is no fixed or universal scientific method (e.g. 1975, 10–11) citing Einstein: “The external conditions which are set for [the scientist] by the facts of experience do not permit him to let himself be too much restricted, in the construction of his conceptual world, by the adherence to an epistemological system. He therefore must appear to the systematic epistemologist as a type of unscrupulous opportunist” (Einstein1949b, 683ff.). Although Feyerabend’s development of the idea of incommensurability of scientific theories was received by the philosophic and scientific communities as propagating a radical, irrationalism about science, he was actually trying to develop ideas he had found in Einstein. In the preface to the German version of Against Method , Feyerabend wrote, “I want to emphasize yet again that the views in this book are not new – for physicist like Mach, Boltzmann, Einstein and Bohr they were a triviality. But the ideas of these great thinkers have been distorted [by positivist philosophers] beyond recognition” (1983, 12, our translation).

Feyerabend tried to clarify his idea of incommensurable scientific theories throughout the 1960s as it became the cornerstone of his peculiar brand of theoretical pluralism explicitly initially developed in contrast to Popper, Kuhn, Putnam and Bohm’s forms of theoretical pluralisms (1962, 32). In Against Method (1975), in addition to the incommensurability of scientific theories and the worldviews they imply, Feyerabend extended the application of this term to characterize the transition from the Greek archaic, aggregate worldview of Homer to the substance worldview of the Pre-Socratics (1975, 261–269). He characterized the wider notion of incommensurability as both historical and anthropological (1975, 271), and he tried to clarify incommensurability by suggesting that it involves major conceptual changes to both ‘overt’ and ‘covert classifications’ (in Whorff’s sense), so that incommensurability is difficult to define explicitly, and can only be shown (1975, 224–225). He also started using the term in much broader senses, discussing incommensurable frameworks of thought and action (1975, 271), incommensurability in the domain of perceptions (1975, 225, 271), incommensurable discoveries and attitudes (1975, 269) and incommensurable paradigms (1981b [1970], 131–161). For Feyerabend, all these cases share the common feature that incommensurability results from the replacement of some form of universal principles.

Initially, Feyerabend had a more concrete characterization of the nature and origins of incommensurability than Kuhn. Feyerabend claimed that the interpretation of an observation language is determined by the theories we use to explain what we observe. When our theories about reality change, what we experience as reality changes accordingly. Kuhn, by contrast, was initially much less sure about the exact meaning of his notion of incommensurability, especially regarding world change, which he saw as its most fundamental aspect. He frankly confessed to have been at a loss: “In a sense that I am unable to explicate further, the proponents of competing paradigms practice their trades in different worlds” (1962, 150). He suggested that “we must learn to make sense of statements that at least resemble these” (1962, 121), and then spent a great deal of effort attempting to do so.

Feyerabend’s discussion of incommensurability of scientific theories was much more restricted than Kuhn’s. For Kuhn, incommensurability had three prima facie heterogeneous domains, holistically bound: a change of problems and standards, a change of concepts used to state and solve them, and a change of worldview in which they arise. Feyerabend’s focus, on the other hand, was initially exclusively on concepts occurring in universal or ‘non-instantial’ theories realistically interpreted. Ironically, however, in developments after 1962, both authors move in opposite directions, converging toward the same views. Kuhn gradually eliminated everything from his notion of incommensurability that does not concern scientific concepts, and ended more or less where Feyerabend began (see Carrier 2001; Chen 1997; Hoyningen-Huene 1990, 487–488; Hoyningen-Huene 1993, 212–218; Hoyningen-Huene 2004, Sankey 1993; Sankey 1994, 16–30; Sankey 1997). Feyerabend, by contrast, increasingly emphasized aspects of perceptual change (1975, 225–229, 273–274; 1978, 68; 1988, 172–176), and also changes to the set of legitimate problems a discipline should handle (1975, 274–275), and in his later philosophy, he emphasizes one of Kuhn’s original points: the role of non-binding, epistemic values in theory choice that can result in ‘methodological’ incommensurability (cf. Farrell 2003).

Concerning the range of theories that are subject to incommensurability, again Feyerabend’s discussion was much more restricted than Kuhn’s. For Feyerabend, only universal , non-instantial theories interpreted realistically can be incommensurable (Feyerabend 1962, 28, fn. 1, 44; 1965b, 216; 1975, 114, 271, 284; 1975, 221–222; 1987, 272). Feyerabend was interested in such theories because he believed that only “such comprehensive structures of thought” have ontological implications that affect entire worldviews (Feyerabend 1962, 28; Feyerabend 1954; cf. Oberheim 2006, 157ff.). He restricted his discussion of incommensurability to non-instantial theories based on their test procedures. Generalizations of the form ‘All A s are B s’ are tested by inspecting instances. For example, Kepler’s first law makes claims about the planets, which can be tested directly by inspecting their motion. To test non-instantial theories, such as Newton’s theory of gravitation, laws or lower-level theories must first be derived from them, and only thereafter (and given additional auxiliary assumptions), can they be tested by inspecting instances (Feyerabend 1962, 28, fn. 1). Feyerabend was talking about relatively rare, large-scale revolutions that affect entire worldviews (1987, 272). In this way, his notion was also more Kantian than Kuhn’s, because Feyerabend (like Kant) was talking primarily about universal theories that determine the meaning of thinghood itself, whereas Kuhn was talking more widely about changes to the meaning of any set of kind terms that break the no-overlap principle. For this reason, Kuhn included a wider range of theories as candidates for incommensurability. For him, even smaller episodes, like unexpected discoveries, might be incommensurable with the earlier tradition (cf. Hoyningen-Huene 1993, 197–201). This difference in the range of incommensurability between Kuhn and Feyerabend’s versions finds its most striking expression in the way they regard the transition from the Ptolemaic to the Copernican theory. For Kuhn, the differences between these two theories comprise an exemplary illustration of incommensurability. For Feyerabend, however, because planetary theory lacks the quality of universality, there is no incommensurability (1975, 114). Furthermore, in his later work, Kuhn insisted that the version of incommensurability he championed had always been “local incommensurability,” a notion that restricts conceptual change to a few, typically interconnected concepts (cf. Hoyningen-Huene 1993, 213, 219). Thus, there may be empirical consequences of incommensurable theory pairs that can be immediately compared. For instance, the geocentric and heliocentric planetary theories are incommensurable in Kuhn’s sense, while predictions of the planetary positions of both theories are fully commensurable, and can be immediately compared regarding their empirical accuracy. By contrast, Feyerabend always thought of incommensurability more globally. Meaning variance in the terms used to state the theories affects the meanings of all statements derivable from those theories about anything and everything so that incommensurable rivals have no formally comparable consequences (1962, 93; 1965c, 117; 1965b, 216; 1975, 275–276; 1981a, xi).

Both Kuhn and Feyerabend have often been misread as advancing the view that incommensurability implies incomparability (cf. Hoyningen-Huene 1993, 218ff.; Oberheim 2006, 235). In response to this misreading, both Kuhn and Feyerabend repeatedly emphasized that incommensurability does not imply incomparability (cf. Hoyningen-Huene 1993, 236ff.). Theory comparison is merely more complicated than imagined by some philosophers of science. In particular, for Kuhn, it cannot fully be made ‘point-by-point’. It is not an algorithmic procedure (cf. Hoyningen-Huene 1993, 147–154; Feyerabend 1975, 114; 1981a, 238), nor one that requires translation into a neutral observation language. Different epistemic values, such as universality, accuracy, simplicity, fruitfulness may pull in different directions allowing for rational disagreement (cf. Hoyningen-Huene 1992, 492–496; 1993, 150–154; cf. Feyerabend 1981a, 16; 1981c, 238). But even given that a full point-by-point comparison of incommensurable theories is impossible and that theory comparison does not have the status of a proof, a comparative evaluation of incommensurable theories is still possible (cf. Hoyningen-Huene 1993, 236–258; Carrier 2001) and rational in a means/ends or instrumental sense. For example, according to Kuhn it is rational to choose theories that are better problem-solvers because they better serve the ends of science. This property of theory choice makes the overall process of science both rational and progressive. With incommensurability, Kuhn was not challenging the rationality of theory choice, he was trying to make room for the possibility of rational disagreement between proponents of competing paradigms. In fact, according to Kuhn, “incommensurability is far from being the threat to rational evaluation of truth claims that it has frequently seemed. Rather, it’s what is needed, within a developmental perspective, to restore some badly needed bite to the whole notion of cognitive evaluation. It is needed, that is, to defend notions like truth and knowledge from, for example, the excesses of post-modernist movements like the strong program” (2000 [1991], 91).

The extent of the misreading of incommensurability as implying incomparability is even more dramatic in Feyerabend’s case. Feyerabend explicitly and repeatedly argued that developing incommensurable rivals offers a better means of testing established theories than merely testing them directly against their own predictions or by developing commensurable alternatives (Feyerabend 1962, 66; cf. Oberheim 2006, 235ff.). They offer a better means of testing because some observations can only be interpreted as refutations of an existing theory after an incommensurable alternative has been developed with which to interpret them (cf. Oberheim 2006, 240–245, Oberheim 2024). The misunderstanding that incommensurability implies incomparability conflates testability with falsifiability, as can be seen in Popper’s The Myth of the Framework (1994). However, Feyerabend was not arguing that universal theories are untestable. He was arguing that they are not falsifiable. He argues that because two incommensurable theories use qualitatively incompatible concepts to interpret quantitatively identical results, they will interpret the same quantitative sentences as different qualitative statements, concluding: “there may not exist any possibility of finding a characterization of the observations which are supposed to confirm two incommensurable theories” (1962, 94, italics inserted). This precludes the possibility of using a neutral observation language (such as Popperian basic statements) for comparing the empirical consequences of rival incommensurable theories by establishing formal relations between them and their corresponding predictions. However, Feyerabend did not conclude from this that they cannot be compared empirically, but rather that there is no need for a neutral observation language to establish formal relations for an empirical comparison, illustrating how with the example of Einstein’s prediction of the stochastic character of Brownian motion. Feyerabend also mentions other possibilities of comparing incommensurable theories and recognizes ‘methodological incommensurability’, although he did not call it that (Feyerabend 1965b, 217; 1970, 228; 1975, 284; 1978, 68; 1981a, 16).

Finally, there is a central, substantive point of agreement between Kuhn and Feyerabend that should be emphasized. Both see incommensurability as excluding the possibility of interpreting scientific development as an approximation to truth (or as an “increase of verisimilitude”) (Feyerabend 1965c, 107; 1970, 220, 222, 227–228; 1975, 30, 284; 1978, 68; Kuhn 1970, 206; 2000 [1991], 95; 2000 [1993], 243ff.; cf. Oberheim 2006, 180ff.; Oberheim 2024; Hoyningen-Huene 1993, 262–264). They reject such characterizations of scientific progress because they recognize that scientific revolutions result in changes to what we experience as real. In scientific revolutions, such changes cannot be just mere refinements of, or additions to, the established theory, such that these developments could be seen as cumulative additions. Rather, the new ontology replaces its predecessor. Consequently, neither Kuhn nor Feyerabend can correctly be characterized as a scientific realist who believes that science makes progress toward truth.

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Scientific Revolution

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The Scientific Revolution (1500-1700), which occurred first in Europe before spreading worldwide, witnessed a new approach to knowledge gathering – the scientific method – which utilised new technologies like the telescope to observe, measure, and test things never seen before. Thanks to the development of dedicated institutions, scientists conducted yet more experiments and shared their knowledge, making it ever more accurate. By the end of this 'revolution', science had replaced philosophy as the dominant method of acquiring new knowledge and improving the human condition.

Defining a 'Revolution'

Dating the beginning and end of the Scientific Revolution is problematic. Historians do not all agree on precise dates as the 'revolution' was not a single dramatic event but, rather, a long and gradual series of discoveries and changes in attitudes to knowledge. The period of the 16th and 17th centuries as a whole generally covers most of the pertinent events and discoveries. There is also the problem of what to call these events. This was not a 'revolution' in the usual sense of the term, that is, a movement involving all classes, in all places, over a short space of time with a defined end goal which was ultimately achieved. Rather, from around 1500 to around 1700, there was a gradual but marked shift in how thinkers approached the acquisition of knowledge of the world around us. Modern historians often shy away from using such a dramatic term as 'revolution' to describe any deep change in human behaviour, since such a blanket term caries with it uncalled-for baggage of meanings and masks a number of anomalies, not least in this case that the 'revolution' was never complete or completed. That something momentous did occur is, however, clear from even the briefest assessment of how knowledge was gathered before and how it has been gathered ever since the Scientific Revolution.

Through the two centuries of the Scientific Revolution, natural philosophers who still adhered to ancient wisdom were slowly replaced in importance by practical scientists who used scientific instruments like the telescope and barometer to test their hypotheses and then share and review their findings. In this way, universal laws could be formed which were then further tested and used to predict outcomes in yet more experiments. Mathematics, in particular, came to dominate thought as more traditional methods of pursuing knowledge like magic, alchemy , and astrology were sidelined in favour of more objective, empirical, and evidence-based experimentation. In addition, the great trio of ancient thinkers who had held sway right through the Middle Ages – Aristotle (l. 384-322 BCE), Claudius Ptolemy (c. 100 to c. 170 CE), and Galen (129-216 CE) – were swept away as early modern minds finally looked to the future instead of the past.

Instruments like the pendulum clock and thermometer made it possible to accurately measure the world around us while optical instruments revealed things previously unimaginable such as the real nature of the surface of the Moon and the intricate anatomy of tiny insects. In all of these senses, then, there was indeed a 'revolution' that resulted in old theories, many of which had been held since antiquity as true, being cast aside and brand new ones replacing them based on new discoveries, new methodologies, and entirely new fields of study.

The Scientific Method

A distinctive feature of the change in thought during the Scientific Revolution was a reconsideration of how new knowledge should be acquired and tested. Practical experiments had been conducted ever since antiquity, but through the Middle Ages, a certain theoretical approach to knowledge, first pioneered by thinkers like Aristotle, had come to dominate. Verbal arguments had become more important than what could actually be seen in the world. Further, natural philosophers had become preoccupied with why things happen instead of first ascertaining what was actually happening in nature and how it was happening. One of the first to question this approach was the English statesman and philosopher Francis Bacon (1561-1626).

Bacon called for a more systematic and practical approach where empirical (observable) consequences of experiments were collated, assessed using reason, and then openly shared for review by other thinkers. The ultimate objective of this activity should be used to test the validity of existing knowledge and forge a new understanding of the world around us so that the human condition can be practically improved. For these reasons, Bacon is considered one of the founders of modern scientific research and scientific method, even as "the father of modern science". Bacon's approach did become a reality, but with important additions such as the use of a hypothesis as part of the experimental process, the application of mathematics to create universal laws, and the addition of new technology that greatly improved the senses.

The scientific method came to involve the following key components:

• conducting practical experiments
• conducting experiments without prejudice of what they should prove
• using deductive reasoning (creating a generalisation from specific examples) to form a hypothesis (untested theory), which is then tested by an experiment, after which the hypothesis might be accepted, altered, or rejected based on empirical (observable) evidence
• conducting multiple experiments and doing so in different places and by different people to confirm the reliability of the results
• an open and critical review of the results of an experiment by peers
• the formulation of universal laws (inductive reasoning or logic) using, for example, mathematics
• a desire to gain practical benefits from scientific experiments and a belief in the idea of scientific progress

(Note: the above criteria are expressed in modern linguistic terms, not necessarily those terms 17th-century scientists would have used since the revolution in science also caused a revolution in the language to describe it.)

Important Inventions

The Scientific Revolution witnessed a great number of new inventions, that is, technological innovations that allowed the new scientists to not only discover new things about the world but also ways to measure, test, and assess these new phenomena. The most important inventions in the Scientific Revolution include:

• the telescope (c. 1608)
• the microscope (c. 1610)
• the barometer (1643)
• the thermometer (c. 1650)
• the pendulum clock (1657)
• the air pump (1659)
• the balance spring watch (1675)

Important Discoveries

With the above inventions and others, scientists in many different countries made many new discoveries, and whole new specialisations of study became possible, such as meteorology, microscopic anatomy, embryology, and optics.

The Italian Galileo Galilei (1564-1642) built the most powerful of the early telescopes, and with it, he discovered the mountains and valleys of the Moon's surface, previously thought to be made of some unknown substance. Galileo identified four moons of the planet Jupiter and the phases of Venus . He observed sunspots, leading him to suggest the Sun was a turning sphere. The German Johannes Kepler (1571-1630) created a new type of telescope, which used two convex lenses, and he used it to observe the heavenly bodies and confirm the heliocentric view of our galaxy proposed by Nicolaus Copernicus (1473-1543 CE). At last, the geocentric model of Ptolemy was shown to be wrong. In addition, Kepler demonstrated that the planets moved in elliptical and not circular orbits.

The Italian astronomer Gian Domenico Cassini (1625-1712) identified the spaces in the rings of Saturn . Johannes Hevelius (1611-1687) in Danzig (modern Gdańsk) discovered the first variable star and created a detailed map of the Moon's surface. The English astronomer Edmond Halley (1656-1742) established an observatory on the island of St. Helena in the South Atlantic in 1677 and created the first chart of the southern stars using a telescope. Halley also discovered the acceleration of the Moon, noted the movement of the stars in relation to each other (proper motion), and identified the comet of 1682 as the same one of 1607 and 1531.

The English scientist Isaac Newton (1642-1727) invented the reflecting telescope in 1668, which used a curved mirror. Newton discovered that white light was made up of a spectrum of coloured light, and he formed his universal theory of gravity, which explained why objects fell on earth and why the heavenly bodies move as they do.

The invention of the microscope, in many ways the natural opposite of the telescope, is usually credited to the spectacle-maker Hans Lippershey (c. 1570 to c. 1619), then living in the Netherlands. The Italian Marcello Malpighi used a microscope to discover capillaries in the blood system in 1661. This was the missing link between arteries and veins, and it confirmed William Harvey's discovery of blood circulation . Galen's views of how the human body worked were now proven to be wholly inadequate or plain wrong.

The English experimentalist Robert Hooke (1635-1703) used his microscope to create sensational drawings of a new miniature world published in his Micrographia in 1665. The Dutchman Antonie van Leeuwenhoek (1632-1723) pioneered a new type of microscope using a glass bead as a lens, which gave him a much greater magnification than previously possible. Leeuwenhoek discovered bacteria, protozoa, red blood cells, spermatozoa, and how minute insects and parasites reproduce. Another Dutch microscopist, Jan Swammerdam (1637-1680), discovered that caterpillars contain what become the wings of the butterfly after metamorphosis. Finally, Nehemiah Grew (1641-1712) was the founder of plant anatomy based on his in-depth study of the sexual organs of plants.

The barometer was invented in 1643 by the Italian Evangelista Torricelli (1608-1647), and it allowed scientists to understand atmospheric pressure. The Frenchman Blaise Pascal (1623-1662) used a barometer to demonstrate that air pressure changes with altitude. The German Otto von Guericke (1602-1686) noted that air pressure varied depending on the weather. The barometer was actually named by the English scientist Robert Boyle (1627-1691), who also worked on air pumps. Boyle and his associate Robert Hooke were able to demonstrate how a vacuum could exist, and they subjected all manner of specimens to changes in air pressure inside their air pump. Boyle was thus able to formulate a universal principle that became known as 'Boyle's Law '. This law states that the pressure exerted by a certain quantity of air varies inversely in proportion to its volume (provided temperatures are constant).

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A related device, the liquid thermometer, was invented in Florence around 1650, and it transformed medicine , allowing doctors to measure a patient's temperature beyond a mere 'hot', 'cold' or 'normal'. The device meant many other experiments could now be made and the results accurately measured and compared.

The first working model of the pendulum clock was invented by the Dutchman Christiaan Huygens (1629-1695) in 1657. In a pendulum clock, the regularity of the pendulum's swing precisely controls the falling of a weight. The best pendulum clocks lost a maximum of 15 seconds per day compared to 15 minutes with a mechanical clock. Timekeeping became even more accurate with the invention in 1675 of watches using a balance spring. This great leap forward in accuracy not only helped scientists better monitor their experiments and time their observations of objects in space but it also revolutionised the very idea of time for everyone. This was the first step towards having a universal time, and with it came the concepts of being early, on time, and late in daily life.

Institutionalised Science

Another key development of the Scientific Revolution, besides a new method and new technology, was the foundation of dedicated research bodies. At this time, universities (with the possible exception of departments of medicine) were not concerned with research, but only with teaching. A new type of institution was required where scientists could work together, share their findings, and, most importantly of all, receive funding for their work. These were the new academies and societies that sprang up across Europe. The first such society was the Academia del Cimento in Florence, founded in 1657. Others soon followed, notably the Royal Society in London in 1663 and the Royal Academy of Sciences in Paris in 1667. Those responsible for the foundation of the Royal Society credited Bacon with the idea, and they were keen to follow his principles of scientific method and his emphasis on sharing and communicating scientific data and results. The Berlin Academy was founded in 1700 and the St. Petersburg Academy in 1724. These academies and societies became the focal points of an international network of scientists who corresponded, read each other's works, and even visited each other's laboratories and observatories as the new scientific method took hold. The public was involved, too, either indirectly through access to published journals and books or directly with the opportunity to attend experiments and demonstrations in the societies' headquarters or out in the field.

That there was an increase in international cooperation in the Scientific Revolution is indicated in the invitation to non-nationals to become fellows of these societies. There were attempts to standardise certain experiments across borders and the instruments different scientists were using. For example, the German Daniel Gabriel Fahrenheit (1686-1736) devised his Fahrenheit scale for thermometers around 1714. Anders Celsius (1701-1744) from Sweden came up with a rival scale, but having two scales on thermometers was a vast improvement from the early days when scientists in different countries simply used their own scales, a situation that made comparisons of results extremely difficult. There was, too, cooperation between scientists despite them belonging to rival European empires, and it was through these colonial empires, especially the Dutch, French, and British, that the ideas of the Scientific Revolution spread far beyond Europe.

Reaction to the Scientific Method

The reaction to the Scientific Revolution was not all positive. Some intellectuals were sceptical that the new scientific instruments could be trusted. There remained sceptics of experimentation in general, those who stressed that the senses could be misled when the reason of the mind could not be. One such doubter was René Descartes (1596-1650), but if anything, he and other natural philosophers who questioned the value of the work of the practical experimenters were responsible for creating a lasting new division between philosophy and what we would today call science. The term "science" was still not widely used in the 17th century, instead, many experimenters referred to themselves as practitioners of "experimental philosophy". The first use in English of the term "experimental method" was in 1675. The development of these terms illustrates that a break was happening between theoretical and practical thinkers.

Some even questioned whether humanity should be delving into a previously unseen world, which they considered should remain God 's affair. There was a clash between science and religion when it came to the view of how the universe was organised. Church figures preferred to hold on to the idea that the Earth and humanity must be at the centre of the universe, and so thinkers like Galileo, who supported Copernicus ' heliocentric model, were found guilty of heresy. However, most scientists were Christians and had no wish to challenge the teaching of the Bible . Many scientists simply wanted to explain how the world was made as it is. Indeed, some argued that the telescope and microscope demonstrated just how intricate life is, and so one should, they thought, hold even more wonder at God's work.

There was still room for God in this new scientific world, since thinkers like Isaac Newton, for example, could only explain that gravity moved planets, he could not explain where gravity came from or why it existed. There were still many limits to human knowledge. Doctors now knew why certain diseases might come about but still had only limited knowledge of how to cure them. The great longitude problem of how navigators could track their position around the globe remained unsolved. Technology was still frustratingly limited in many areas.

Into the Future

New scientific instruments meant that discoveries came thick and fast, often causing bewilderment at just how complex life could be. Telescopes at one end of the scale and microscopes at the other revealed that a whole new system of measurement was required for the human mind to grasp the scale of the wonders of the visible universe. Previously, the human body had been used as a base of the measurement system, soon nanometers and light years would be required. There were momentous changes in how people of all classes viewed the new worlds opened up by the scientists. This is best seen in the popular fiction of the period, which began to discuss intriguing yet also troubling ideas like the infinity of the universe or that tiny parasites themselves had even smaller parasites, which themselves had yet smaller parasites. Could it be possible to one day travel to the Moon? Since the Earth was no longer the centre of the universe, did this not mean there could be other planets with other life forms?

There was, though, amongst this perplexity, a new confidence and belief, certainly amongst the scientists, that technology and science, given time, could provide all the answers humanity needed to live better, longer, and more happily. New clock mechanisms with their sophisticated gears, the use of pistons in air pumps, and the discovery of the power of air pressure all inspired engineers to invent new machines like the steam engine as another, even greater revolution, appeared on the horizon: the British Industrial Revolution .

The Scientific Revolution had another lasting effect, and that is the establishment of science as the most recognised method of finding truth, a position of dominance it still holds today. When we talk about theories, hypotheses, laws of nature, evidence, facts, and progress we use terms which were coined during the Scientific Revolution; to discuss knowledge today without using these terms is unthinkable, and there, perhaps, lies the true legacy of this revolution in ideas, methods, and technology.

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Bibliography

• Burns, William E. The Scientific Revolution in Global Perspective. Oxford University Press, 2015.
• Burns, William E. The Scientific Revolution. ABC-CLIO, 2001.
• Bynum, William F. & Browne, Janet & Porter, Roy. Dictionary of the History of Science . Princeton University Press, 1982.
• Fermi, Laura & Bernardini, Gilberto. Galileo and the Scientific Revolution. Dover Publications, 2013.
• Gleick, James. Isaac Newton. Vintage, 2004.
• Henry, John. The Scientific Revolution and the Origins of Modern Science . Red Globe Press, 2008.
• Jardine, Lisa. Ingenious Pursuits. Nan A. Talese, 1999.
• Wootton, David. The Invention of Science. Harper, 2015.

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91 Scientific Revolution Essay Topic Ideas & Examples

🏆 best scientific revolution topic ideas & essay examples, 📌 good essay topics on scientific revolution, 🔎 simple & easy scientific revolution essay titles, ❓ questions about the scientific revolution.

• The Impact of Scientific Revolution on Christianity Questioning the supremacy of church as the most powerful institution in the Western society, the scientific advances revolutionized the existing system of knowledge and became an important player in exploring the phenomena of the surrounding […]
• Thomas Kuhn’s “The Structure of Scientific Revolutions” He adds on to say that Kuhn’s analysis of the scientific revolution does not provide a reality of understanding the world in the context of science.
• Overview of the Scientific Revolution Periods The supporters of humanistic theory agree with the ideas of great influence of people on the development of science. The emergence of the Western culture has given rise to the development of new directions of […]
• Thomas Kuhn’s Scientific Revolution The implicit assumptions of a paradigm act as criterion that is used in study or to validate study. A paradigm shift is a radical change in the way science as a study and criterion for […]
• Excerpt from the Structure of Scientific Revolutions In the case of psychology, the discipline has yet to settle on a single dominant paradigm, leading to a continued evolution of the field and a lack of a shared understanding of its basic foundations.
• Scientific Revolution and Its Consequences Engaging humans in scientific processes and achievements can help decrease the firmness of their beliefs and give them a chance to technological progress.
• The Scientific Revolution as the Greatest Achievements by the Humanity The Scientific Revolution can be explained as a historic phenomenon which occurred between The Enlightenment and the beginning of industrialization in the end of the eighteenth century.
• The Role of Galileo in Scientific Revolution In an article by Little Edmund on Galileo, science, and the church, the writer clearly shows us that the church was hostile towards science and scientific facts.
• The Structure of Scientific Revolutions Understanding scientific objectivity is vital to considering the validity of gained evidence and the possible influences that may sway the conclusions of the study.
• “The Structure of Scientific Revolutions” by Kuhn A scientific paradigm may be defined as a set of discoveries and achievements recognized and accepted by the scientific community at a given moment in time.
• Scientific Revolution and Enlightenment The emergence of shared spaces open to scientific debate contributed to the propagation of the inquiring spirit of the era, which helped to shape the cultures of many European states.
• “The Structure of Scientific Revolutions” by Thomas Kuhn Thus, it can be argued that the process of dislodging a scientific paradigm by a new one is congruous with a nonrelativistic approach.
• Scientific Revolution’ Study for 7th Grade Students At the age of 12-14, children are learning to analyze and evaluate their knowledge, which is why the overarching goal of a middle-school world history course is to teach children to think like historians. The […]
• Galileo Galilei and His Role in the Scientific Revolution Galileo’s later discoveries of the Venus gave more proof to the Copernicus theory that it is the Sun at the centre of the universe and not the Earth.
• Scientific Revolution History: Attitude of Mechanization The above statement refers to the modernization as enshrined in the need for empirical inference as an exponential factor of knowledge creation and dispersion.
• History: Evolution of the Scientific Revolution The onset of the scientific revolution is associated with Copernican technical inventions of 1543 and the discovery of motion science by Galileo.
• The Significance of Scientific Revolution in Our History People used religion to explain the happenings of and within the universe by viewing the universe as godly beginning with nothing to do with scientific development.
• Historiography of Science and the Scientific Revolution His contribution to the field of philosophy of science resulted in a paradigm shift on various aspects of positivists’ doctrine and insights into the history of science1.
• Why the Scientific Revolution did not Take Place in China–Or Did It? The history of science and technology in China contributed much to the advancement of the global knowledge in science and technology.
• Thomas Kuhn’s Scientific Revolutions However, Kuhn notes that, this process of reconstructing and reconsidering assumptions and facts is tedious and time consuming; therefore, he offers a way of creating paradigms in the process of scientific revolution.
• The History of Humanities Scientific Revolution Therefore, the need to strengthen natural science as an independent discipline led to the establishment of scientific societies such as the Accademia del Cimento, the Academie des Sciences, and the Royal Society of London, which […]
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• The Personalities That Contributed to the Changes During the Scientific Revolution
• Political Factors of the Scientific Revolution
• The Scientific Revolution and Its Effect on Religion
• How Did the Scientific Revolution Lead to the Enlightenment
• Intellectual Revolution Resulting From Scientific Revolution
• What Major Changes Occurred During the Scientific Revolution in the 17th Century?
• How Did the Scientific Revolution and Enlightenment Shape the Industrial Revolution?
• What Were the Roots of the Scientific Revolution?
• How Did the Scientific Revolution Affect Many Aspects of Life in Europe?
• Was the Scientific Revolution a Real Threat to Western Christian Values?
• What Were the Causes and Effects of the Scientific Revolution and How Did It Change the World in the Years 1500–1800?
• How Did the Renaissance, the Reformation, and the Scientific Revolution Lead to a More Secular and Democratic Society?
• What Was the Contribution of Francis Bacon to the Scientific Revolution?
• How Did Isaac Newton Start the Scientific Revolution?
• Was There Any Connection Between Religion and Science in the Scientific Revolution?
• What Is the Relationship Between the Development of the Enlightenment and the Scientific Revolution?
• How Did Scientists and Philosophers Change Medieval Ideas About Science and Natural Law During the Scientific Revolution?
• What Personalities Contributed to the Changes During the Scientific Revolution?
• Did the Scientific Revolution Affect Religion?
• Who Were the Supporters and Opponents of the Scientific Revolution?
• What Was the Role of Women During the Scientific Revolution?
• How Did the Scientific Revolution Create the Environment for the Enlightenment?
• What Was the Impact of the Scientific Revolution on Western Perspectives?
• How Did the Scientific Revolution Affect People’s Beliefs?
• What Were the Intellectual, Social, and Religious Consequences of the Scientific Revolution for the West?
• Are There Connections Between the Scientific Revolution and the French Revolution?
• Was the Scientific Revolution Mainly the Result of Technological Advances from the Renaissance?
• What Did the Scientific Revolution Bring to the European World?
• How Did the Scientific Revolution Change Productivity in Western Industry?
• What Was the Social Paradigm of Change Represented by the Scientific Revolution?
• How Did the Scientific Revolution Affect People’s View of the Catholic Church?
• Why Was the Scientific Revolution in Europe and Not in China?
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Bibliography

IvyPanda . "91 Scientific Revolution Essay Topic Ideas & Examples." February 29, 2024. https://ivypanda.com/essays/topic/scientific-revolution-essay-topics/.

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How the Protestant Reformation set the stage for the Scientific Revolution

• The Protestant Reformation is often thought of as mostly a dispute between theologians. 
• In actuality, the Reformation was a full-fledged revolution, toppling Europe’s mightiest powers and setting the stage for the Scientific Revolution. 
• As Friedrich Engels put it in 1850, there is little difference between the struggles of medieval reformers and those of modern-day revolutionaries. 

During the 16th century, preachers and theologians across Europe came together to voice their dissatisfaction with the Catholic Church, which they believed had strayed from the original teachings of Jesus Christ as outlined in the New Testament. They published pamphlets using the printing press, a new invention, and translated the Bible into vernacular languages so all could read it. 

The Protestant Reformation, as their movement became known, proved too difficult for the conservative popes and cardinals to contain. Just a few short years after the German priest and professor of moral theology Martin Luther published his famed Ninety-Five Theses , the Christian faith, unified for much of the Middle Ages, split into various factions. 

Nowadays, many view the Protestant Reformation as a conflict that took place only on paper: a contrived and somewhat supercilious argument between theologians and academics that may have changed the organization of religious institutions but, at least in the long run, had little impact on the way that ordinary people lived their lives. 

This is a misconception. The Catholic Church was the single most influential force in the medieval world. Dismantling its centuries-long hegemony was no easy feat, and its fall from grace ushered in a whole new age. The Reformation’s political and economic ramifications are on par with revolutions in France, Russia , and America and deserve to be studied with the same interest. 

The economics of the Protestant Revolution

The economic consequences of the Protestant Reformation were first brought to the academic community’s attention by sociologist Max Weber. Living in Prussia, Weber noticed that Protestant cities tended to be more affluent than Catholic ones, leading him to reflect on the possible correlations between Protestantism and prosperity. 

In his 1905 book, The Protestant Ethic and the Spirit of Capitalism , Weber argues the Reformation and economic success were causally linked. His thesis has been confirmed by many studies, including one by economists Sascha Becker and Ludger Woessman , who looked at data from 452 counties in Prussia from 1871 and concluded that Protestants had a significantly higher income than Catholics. 

Although the literature concurs with the crux of Weber’s argument, there is some disagreement on which aspects of Protestantism are conducive to having a higher income. Weber identified two economically beneficial qualities that the austere Luther helped inspire in his followers: a tireless work ethic and an entrepreneurial spirit. 

“The ability of mental concentration,” Weber wrote in The Protestant Ethic , “as well as the absolutely essential feeling of obligation to one’s job, are here most often combined with a strict economy which calculates the possibility of high earnings, and a cool self-control and frugality which enormously increase performance.”

How Martin Luther kickstarted the book trade

Becker and Woessman settled for a different explanation. According to them, the Protestant Reformation boosted Europe’s economy by improving literacy rates. For much of the Middle Ages, clergymen were the only members of society who were taught to read and write and did so in a language only they could comprehend : Latin.

This gave the Catholic Church exclusive access to Christian texts, allowing it to operate as an intermediary between man and God. Luther, aligning himself with an earlier reformer named John Wycliffe, believed religious wisdom should be accessible to everyone. To that end, he translated the New Testament into German, the same language in which he wrote his most influential work. 

So great was Luther’s impact on literacy in Germany that, without him, the country’s printing industry may well have died off in its infancy. In a 2016 lecture , historian Andrew Pettegree explains how the preacher’s steadily growing readership helped turn his home base of Wittenberg from a sleepy, destitute town into an economic center, at least as far as the book trade was concerned. 

“Printers got an immediate return for minimum investment,” Pettegree exclaims. “Luther, it very quickly became clear, was a safe bet for the printing industry.” His own book, Brand Luther , frames the preacher as the world’s first media personality. Luther’s popularity with readers shaped the modern book trade, paving the way for numerous philosophers, scientists, and authors.

Ending the monopoly of the Catholic Church

Most contemporary economists are of the opinion that competition is essential to economic development because it encourages innovation and efficient allocation of resources. For this very reason, they argue governments should try to create free market economies that encourage competition and, where possible, discourage the formation of monopolies.

This was certainly not the case in the Middle Ages, a time when the Catholic Church was as prosperous as it was powerful. A political force, the Church persecuted heretics and excommunicated kings. The Church was also not required to pay any taxes, meaning it could hoard an unprecedented amount of wealth through tithes and indulgences — the absolution of sin in exchange for silver pennies. 

Like anyone who engages in rigorous Bible study, Luther came to disagree with the idea that sin could be forgiven through payment. His Ninety-Five Theses argued that salvation was, by definition, free, but that it could be attained only through the personal and unmediated contemplation of Christ’s wisdom. His Theses , in essence, ended the Church’s monopoly over the afterlife. 

Luther’s victory over the Church introduced new degrees of religious freedom. The unhindered exchange of ideas that flowed from this freedom laid the foundation for the Scientific Revolution. Economists have also determined that the Reformation “produced rapid economic secularization,” creating a “shift in investments in human and fixed capital away from the religious sector.”

The political legacy of the Radical Reformation

Like any revolution, the Protestant Reformation was not a unified movement but a collection of increasingly divergent factions organized around seemingly irreconcilable beliefs. Luther, historians now concur, belonged to the Magisterial Reformation, a group campaigning for the separation between church and state while also maintaining good relations with secular rulers. 

There was also another, smaller faction. Members of this faction , now referred to as the Radical Reformation, sympathized with the struggle of Luther, Ulrich Zwingli, and John Calvin. However, they also believed that these comparatively moderate reformers had made several concessions which stopped short of addressing the issues plaguing the Christian faith. Taking ideas in Luther’s Ninety-Five Theses to their extreme, the Radical Reformation came to the following conclusion: because the grace of God could only be attained through personal, unmediated contemplation, the sheer concept of organized religion was nonsensical and a deviation from pure Christianity as depicted in the New Testament. 

Unsurprisingly, a focus on autonomy and aversion to organization splintered the Radical Reformation. Still, commonalities emerged among different sub-groups. Luther and Calvin were likened to the popes they rebelled against. Radical reformers also rejected infant baptism, claiming a person should come into the faith by their own choice, not by accident of birth . 

Thomas Müntzer’s proto-communism

Some reformers sought to change not just religious institutions but secular ones as well. Thomas Müntzer was a preacher, theologian and, toward the end of his life, a commander in the German Peasants’ War of 1525, leading an inspiring but unsuccessful rebellion against the princes of the Holy Roman Empire, a political entity Müntzer considered anything but sanctified. 

Müntzer’s argument was simple, simpler even than Luther’s. His only axiom, namely that “you cannot serve both God and money,” was more than a denunciation of Catholic indulgences; it was a call for the destruction of class-based society in general. After all, in a world created by God, there was no place for feudal lords; their mere existence was a violation of His will. 

While Luther — a longtime friend and ally of Saxony’s ruler Frederick the Wise — published a pamphlet titled Against the Robbing and Murdering Hordes of Peasants , Müntzer was defeated, captured, tortured, and executed for treason. Though he was not nearly as influential as Luther, the radical reformer still left his mark on history, albeit several centuries after his death. 

In 1850, Friedrich Engels wrote The Peasant War in Germany , which draws parallels between the Protestant Reformation and 19th century revolts against European monarchies. Engels saw Müntzer as a precursor to the communists, showing us that “still the peasant war is not as far removed from our present-day struggles… and the opponents we have to encounter remain essentially the same.”