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Kuhn, Thomas Samuel


(b. Cincinnati, Ohio, 18 July 1922; d. Cambridge, Massachusetts, 17 June 1996),

philosophy of science, history of science, concept of paradigm.

A physicist turned historian of science for philosophical purposes, Kuhn was one of the most influential philosophers of science in the twentieth century. In his famous book The Structure of Scientific Revolutions, first published in 1962, Kuhn helped destroy the popular image of science according to which science steadily and incrementally progresses toward a true and complete picture of reality. Relying on historical case studies, Kuhn argued that, ruptured by scientific revolutions, scientific

development was discontinuous and noncumulative and that scientific activity before and after a revolution was in some ways incommensurable, lacking a common measure. In this way Kuhn not only formed a startling picture of science, but also initiated a new way of doing philosophy of science informed by the history of science.

Life and Career . Thomas Kuhn was the son of Samuel L. Kuhn, who was trained as a hydraulic engineer at Harvard University and the Massachusetts Institute of Technology (MIT), and Annette Stroock Kuhn. Both parents were nonpracticing Jews. Kuhn attended several schools in New York, Pennsylvania, and Connecticut. Among them, Hessian Hills in Croton-on-Hudson, New York, a progressive school that encouraged independent thinking, made a particularly strong impression on him. He then attended Harvard University, graduating summa cum laude with a degree in physics in 1943. Despite the fact that his interest lay in theoretical physics, most of his coursework was in electronics, due to the orientation of his department. His professors included George Birkhoff, Percy W. Bridgman, Leon Chaffee, and Ronald W. P. King. He also took several elective courses in social sciences and humanities, including a philosophy course in which Immanuel Kant struck him as a revelation. He did not enjoy the history of science course that he attended, which was taught by the famous historian of science George Sarton.

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. He also took a few philosophy courses in order to explore other possibilities than physics. It was about this time that the legendary president of Harvard University, the chemist and founder of “Harvard Case Studies in Experimental Science” James Conant, asked Kuhn to assist his course on science, designed for undergraduates in humanities as part of the General Education in Science Curriculum. This event changed Kuhn’s life. His encounter with classical texts, especially Aristotle’s Physics, was a crucial experience for him. He realized that it was a great mistake to read and judge an ancient scientific text from the perspective of current science and that one could not really understand it unless one got inside the mind of its author and saw the world through his eyes, through the conceptual framework he employed to describe phenomena. This understanding shaped his later historical and philosophical studies.

In 1948 Kuhn became a junior member of the Harvard Society of Fellows upon Conant’s recommendation. A year later, he completed his PhD in physics under the supervision of John H. van Vleck, who won the Nobel Prize in 1977. Kuhn became an assistant professor of general education and the history of science in 1952 and taught at Harvard until 1956. During this period he trained himself as a historian of science, and Alexandre Koyré’s works, especially his Galilean Studies, had a deep impact on him.

Between 1948 and 1956, Kuhn published three articles, one with van Vleck on computing cohesive energies of metals, derived from his PhD dissertation, and a number of historical works on Isaac Newton, Robert Boyle, and Sadi Carnot’s cycle. He also wrote his first book, The Copernican Revolution, which was published in 1957. Nevertheless, Kuhn was denied tenure because the review committee thought that the book was too popular and not sufficiently scholarly.

Feeling disappointed, Kuhn accepted a joint position as an assistant professor in the history and philosophy departments at the University of California, Berkeley. Soon after, he published his masterpiece, The Structure of Scientific Revolutions. It was also here that he met Paul Feyerabend, who introduced a version of the thesis of incommensurability at the same time Kuhn did. But the interaction was not fruitful. The person who influenced him most at Berkeley was Stanley Cavell. Cavell introduced him to the philosophy of Ludwig Wittgenstein, whose view of meaning as use and idea of family resemblance had a lasting influence on Kuhn. He also heard Michael Polányi’s lectures on tacit knowledge, a notion that also found its way into his influential book.

Between 1961 and 1964 he headed a project known as the “Sources for History of Quantum Physics,” which contained interviews with, and manuscript materials of, all the major scientists who contributed to the development of quantum physics. These materials are now part of the Archive for History of Quantum Physics.

Kuhn was offered a full professorship at Berkeley in history, not in philosophy. Although disappointed, he accepted the offer. Not long after, however, he left Berkeley for the position of M. Taylor Pyne Professor of Philosophy and History of Science at Princeton University. He taught at Princeton from 1964 to 1979 and then, because of his divorce, he left Princeton and joined the philosophy department at MIT. In 1982 he was appointed to the Laurence S. Rockefeller Professorship in Philosophy, a position he held until 1991 when he retired. He became professor emeritus at MIT from then on until his death. He was survived by his second wife Jehane, his ex-wife Kathryn Muhs, and their three children.

Thomas Kuhn received the Howard T. Behrman Award for distinguished achievements in the humanities (1977), the History of Science Society’s George Sarton Medal (1982), and the Society for Social Studies of Science’s John Desmond Bernal Award (1983). He was a Guggenheim Fellow during 1954 to 1955, a member of the Institute for Advanced Study in Princeton (1972–1979), a member of the National Academy of Sciences, and a corresponding fellow of the British Academy. He also held honorary degrees from Columbia, Chicago, and Notre Dame universities in the United States, the University of Padua in Italy, and the University of Athens in Greece. He was the only person to have served as presidents of both the History of Science Society (1968–1970) and the Philosophy of Science Association (1988–1990).

The Structure of Scientific Revolutions . The Structure of Scientific Revolutions (Structure for short) opens with the sentence, “History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed” (1970, p. 1). According to that image, science progresses toward truth in a linear fashion, each new theory incorporating the old one as a special case. Scientific progress is due to the scientific method, whereby theories are tested against observations and experiments; those that fail are disconfirmed or get eliminated and those that pass the tests are considered to be confirmed, or at least not yet falsified.

This image was very popular among scientists, and in the philosophical world it was represented in various forms by logical positivists such as Rudolf Carnap, who emphasized confirmability and by Karl Popper, who emphasized falsifiability. Most logical positivists, though emphatically not Popper, also believed that observation provided neutral and secure grounds for the appraisal of scientific theories. It was generally agreed that scientific rationality and objectivity was a matter of compliance with the rules of scientific method, leaving little room for individual choices. Although Structure contained only one explicit reference to Popper and none to the logical positivists, clearly it targeted them, and together with the works of Norwood Hanson, Paul Feyerabend, and Stephen Toulmin, it destroyed the existing conception of science and scientific change.

The main thesis of Kuhn’s book was that development in mature sciences typically goes through two consecutive phases: normal and revolutionary. Normal science is a paradigm-governed activity of puzzle solving. Based on settled consensus of the scientific community, normal scientific activity has little room for novelty that transcends the bounds of the paradigm. A paradigm provides a concrete model (called an “exemplar”) for solving problems it has set out. Kuhn called these problems “puzzles” because the paradigm assures the members of the scientific community that with sufficient skill and ingenuity they can be solved within its resources. Thus, in case of failure to solve a puzzle it is the individual scientist, not the paradigm, that is to be blamed. When, however, puzzles resist persistent attempts at solution, they turn into anomalies; and anomalies lead to a crisis when they accumulate. Crisis is marked by a loss of confidence in the paradigm and a search for an alternative one. Rival accounts proliferate, the most fundamental commitments about nature get questioned, and in the end, the scientific community embraces the most promising alternative as the new paradigm. A scientific revolution has occurred. Consequently, a new period of normal science begins, and a similar cycle of normal science–crisis–revolution follows.

Whereas normal science is cumulative, revolutionary science is not. The new paradigm and the activity governed by it are in many ways incompatible with the old one. Kuhn expressed this point in terms of the thesis of incommensurability, which has several aspects. Both problems and the way they are solved change: there is a conceptual change, whereby certain terms acquire new meanings; because every observation is theory-laden, there is a perceptual change, a Gestalt switch, which causes the scientists to see the world differently; and, finally, there is even a sense in which the world itself changes after a revolution. For instance, according to Kuhn, the Aristotelian world contains swinging stones, but no pendulums. Accordingly, whereas the Aristotelian scientist sees constrained motion in a swinging stone, the Galilean-Newtonian scientist (who may as well be a transformed Aristotelian) literally sees a pendulum. In short, the new paradigm is incommensurable with the old one.

Scientists working under rival paradigms often talk past each other and experience a breakdown in communication. The switch from one paradigm to another is very much like a conversion experience rather than a rational choice dictated mechanically by scientific methodology. Furthermore, much that has been accepted as true is discarded, making it impossible to say that the new paradigm brings us closer to truth.

Not surprisingly, Structure sent shock waves through the philosophical community. Kuhn was accused of robbing science of its rationality and objectivity, turning it into a kind of mob psychology; he was charged with relativism, subjectivism, and outright idealism. Normal science was said to be dangerously dogmatic. The notion of “paradigm” was held to be too vague, lacking a definite meaning.

In the “Postscript” to Structure, which was added to the second edition in 1970, and in several subsequent articles, most notably “Objectivity, Value Judgment, and Theory Choice,” collected in The Essential Tension, published in 1977, Kuhn defended himself against these charges, clarifying some of his earlier statements and retracting others. In this context the first thing he did was to clarify what he meant by “paradigm,” for which he now preferred the term “disciplinary matrix.” A disciplinary matrix consisted of four elements: metaphysical commitments; methodological commitments; criteria such as quantitative accuracy, broad scope, simplicity, consistency, and fruitfulness (which Kuhn called “values” since they are desired characteristics of scientific theories); and exemplars.

The most important of these is exemplars, that is, concrete problem solutions that serve as models. Exemplars are always given in use; they guide research even in the absence of rules; and the study of exemplars enables scientists to acquire an ability to see family resemblances among seemingly unrelated problems. Much knowledge that is acquired in this way is tacit, inexpressible in propositions. Normal science is dogmatic to some degree, since it does not allow the questioning of the paradigm itself, but this sort of dogmatism is functional: it allows the scientists to further articulate their paradigmatic theory and pay undivided attention to the existing puzzles and anomalies, the recognition of which is a precondition for the emergence of novel theories and subsequently a revolution. In this way Kuhn dispelled the charges of vagueness and dogmatism.

He also took pains to argue that incommensurability, the target of the greatest outrage, did not necessarily imply incomparability. Two paradigms, he said, often share enough common points to make it possible to compare them. For example, the astronomical data regarding the position of Mercury, Mars, and Venus were shared by both the Aristotelian-Ptolemaic and Copernican paradigms, and they both appealed to similar criteria (“values”). These commonalities provided sufficient grounds for paradigm comparison.

Kuhn pointed out, however, that two scientists working under rival paradigms may share the same criteria but apply them differently to concrete cases. When they are confronted with a new puzzle, they may disagree, for instance, about whether paradigm A or B provides a simpler solution, or they may attach different weights to the shared criteria. This is a perfectly rational disagreement, and the only way to resolve it is through the techniques of persuasion. It is for this reason that paradigm choice often involves subjective, though not arbitrary, decisions.

Rather than denying rationality, Kuhn developed a new conception of it. For him rationality is not just a matter of compliance with methodological rules. This is because the knowledge of how to apply a paradigm to a new puzzle is mostly learned not by being taught abstract rules but by being exposed to concrete exemplars. Yet this is a kind of tacit knowledge that is almost impossible to detach from the cases from which it was acquired. Thus, both paradigm choice and paradigm application often involve judgment and deliberation, a process akin to Aristotle’s phronesis; each scientist must use her lifelong experience, her “practical wisdom,” to make the best possible decision. In short, Kuhn urged a shift from a conception of rationality based on the mechanical application of determinate rules to a model of rationality that emphasizes the role of exemplars, deliberation, and judgment.

Kuhn also argued that science does progress, but not toward truth in the sense of correspondence to an objective reality, because later theories are incommensurable with the earlier ones. Scientific progress for Kuhn simply meant increasing puzzle-solving ability: later theories are better than earlier ones in discovering and solving more and more puzzles. Appealing to the existence of shared criteria for paradigm comparison and to an instrumental idea of scientific progress, Kuhn tried to defend himself against the charge of relativism.

The Linguistic Turn . In the 1980s and 1990s Kuhn wrote a number of articles, reformulating most of his philosophical views in terms of language, more specifically in terms of what he called taxonomic lexicons. These articles were published posthumously in the collection The Road since Structure (2000) and can be summarized as follows.

First of all, having abandoned the terms disciplinary matrix as well as the much-used and -abused term paradigm in favor of theory, Kuhn now underlined the point that every scientific theory has its own distinctive structured taxonomic lexicon: a taxonomically ordered network of kind-terms, some of which are antecedently available relative to the theory in question.

Second, lexicons are prerequisite to the formulation of scientific problems and their solutions, and descriptions of nature and its regularities. Hence, revolutions can be characterized as significant changes in the lexicons of scientific theories: both the criteria relevant to categorization and the way in which given objects and situations are distributed among preexisting categories are altered. Since different lexicons permit different descriptions and generalizations, revolutionary scientific development is necessarily discontinuous.

Third, the distinction between normal and revolutionary science now becomes the distinction between activities that require changes in the scientific lexicon and those that do not. Revolutions involve, among other things, novel discoveries that cannot be described within the existing lexical network, so scientists feel forced to adopt a new one. The earlier mentalistic description (i.e., Gestalt switches and conversions) disappears from Kuhn’s writings.

Finally, incommensurability is reduced to a sort of untranslatability, localized to one or another area in which two lexical structures differ. What gives rise to incommensurability is the difference between lexical structures. Because rival lexical structures differ radically, there are sentences of one theory that cannot be translated into the lexicon of the other theory without loss of meaning. All other aspects of incommensurability that were present in Structure drop out.

Kuhn also gave a Kantian twist to these ideas. He argued that structured lexicons are constitutive of phenomenal worlds and possible experiences of them. In Kuhn’s view a taxonomic lexicon functions very much like the Kantian categories of the mind. This in turn led him not only to embrace a distinction between noumena and phenomena, but also to claim that fundamental laws, such as Newton’s second law, are synthetic a priori. The sense of a priori Kuhn had in mind is not “true for all times,” but something like “constitutive of objects of experience.” This is a historical or relativized a priori, like Hans Reichenbach’s. Taxonomic lexicons do vary historically, unlike Kantian categories. Even the second law is revisable despite the fact that it is recalcitrant to refutation by isolated experiments. Accordingly, Kuhn’s final position can be characterized as an evolutionary linguistic Kantianism.

Using first principles, as it were, regarding the structure of taxonomic lexicons of scientific theories, and having a developmental perspective not simply derivative from the historical case studies, Kuhn’s linguistic turn enabled him to refine, add to, and unify his earlier views about scientific revolutions, incommensurability, and exemplars. He was also able to explain more clearly why incommensurability does not imply incomparability and why communication breakdown across a revolution is always partial. This is because incommensurability is a local, not global, phenomenon pertaining to a small subset of the scientific lexicon, and whatever communication breakdown exists can be overcome by becoming bilingual.

Furthermore, he was finally able to articulate the sense in which the scientist’s world itself changes after a revolution. That sense is Kantian. Whereas the noumenal world is fixed, the phenomenal world constituted by a lexicon is not. Different lexicons “carve up,” as it were, different phenomenal worlds from the unique noumenal world, so Kuhn could now respond to the charge of idealism by pointing out that the noumenal world does exist independently of human minds, though it remains unknowable.

History of Science . In the background of The Structure of Scientific Revolutions is The Copernican Revolution, Kuhn’s first major contribution to the historiography of science. That book grew out of Kuhn’s science course for the humanities at Harvard in the 1950s and provided one of the key historical case studies that later enabled him to articulate his views about the development of science. The Copernican Revolution achieved several things at once. It showed above all that Nicolaus Copernicus was both a revolutionary and a conservative at the same time. Contrary to popular belief, the Copernican heliocentric system, with its rotating spheres, perfectly circular orbits, epicycles, and eccentricities, was in many ways a continuation of the Aristotelian-Ptolemaic tradition of astronomy. But this conservativeness also meant that the Aristotelian-Ptolemaic tradition was a respectable scientific enterprise, having its own conceptual framework, problems, and ways of solving them. When looked at retrospectively, however, the Copernican system did pave the way, albeit unintentionally, for a revolution in science through the works of Johannes Kepler, Galileo Galilei, and Newton.

Kuhn argued forcefully in his book that aesthetic considerations played an important role in Copernicus’s placing the Sun at the center and thus turning Earth into an ordinary planet; the Ptolemaic system looked increasingly complicated, indeed “monstrous,” in the eyes of Copernicus. Although his model did not automatically yield simpler calculations, it provided qualitatively more coherent interpretations of certain phenomena, notably, the retrograde motion of planets. In addition to these, Kuhn drew attention to social factors behind the Copernican Revolution as well, such as the need for calendar reform, improved maps, and navigational techniques. Kuhn also pointed out the larger ramifications of the heliocentric system—in particular, how it changed the conception human beings had of their unique place in the universe and what sense that conception had for them.

After The Copernican Revolution, Kuhn wrote a number of influential historical articles, including one on energy conservation as an example of simultaneous discovery, one on the difference between mathematical and experimental (dubbed as “Baconian”) traditions in the development of physical sciences, and another, with John Heilbron, on the genesis of the Bohr atom. Most of these are conveniently collected in his book The Essential Tension.

Kuhn’s final major contribution to the historiography of science was his controversial book Black-Body Theory and the Quantum Discontinuity, 1894–1912, published in 1978. It constituted a break with a longstanding historio-graphical tradition and undermined the consensus between physicists and historians that quantum physics originated in the works of Max Planck in 1900. According to the traditional interpretation, Planck was forced to introduce the idea of energy quanta, thus breaking with classical physics. More sophisticated versions of this interpretation, which recognized that Planck himself did not understand the exact meaning of the energy quanta, were also defended in various forms by historians of science. In his book Kuhn argued that Planck did not abandon the framework of classical physics until after Hendrik Lorentz, Paul Ehrenfest, and Albert Einstein in 1905 attempted to understand his theory of blackbody radiation.

Of the two historical books Kuhn wrote, the earlier one became a small classic of its own. Historians criticized the second one for exaggerating its case and ignoring certain developmental aspects of Planck’s works, and philosophers were surprised that it did not contain any references to “paradigms,” “normal science,” “incommensurability,” and the like. Kuhn defended himself in the second edition, arguing that many of the themes of Structure were there, though implicitly.

Kuhn wore two hats, but never simultaneously. He saw the history and the philosophy of science as interrelated but separate disciplines with different aims. He believed that no one could practice them at the same time. As a philosopher, he said, he was interested in generalizations and analytical distinctions, but as a historian he was trying to construct a narrative that was coherent, comprehensible, and plausible. For this latter task, the historian had to pay attention first to the factors internal to science, such as ideas, concepts, problems, and theories, and to external factors like social, economic, political, and religious realities. In his historical works Kuhn focused primarily (but not exclusively) on the internal factors, but believed that although the internal and the external approaches were autonomous, they were complementary. He saw the unification of them as one of the greatest challenges facing the historian of science.

Impact . Kuhn’s immense impact on the philosophy of science was exclusively through his works, since he did not supervise any PhD theses in this field. He did have, however, a number of PhD students in the history of science, including John Heilbron, Norton Wise, and Paul Forman, though Forman, in the end, completed his PhD thesis officially under Hunter Dupree.

In historiography of science, Kuhn was a first-rate practitioner of the approach inaugurated by Alexandre Koyré, whom he admired deeply. Following Koyré, Kuhn believed that understanding a historical text necessarily involves a hermeneutical activity by which the historian interprets the text in its own terms and intellectual context. This means that the history of science should always be seen as part of the history of ideas, wherein the aim is to produce a maximally coherent interpretation. The historian is not someone who merely chronicles who discovered what and when. The projection of current conceptions onto past events is a cardinal sin often committed by the earlier positivistically inclined generations of historians of science, including Sarton. In the hands of Koyré, Kuhn, Rupert Hall, Bernard Cohen, Richard Westfall, and others, a new way of practicing historiography of science emerged. As a result, the Scientific Revolution of the sixteenth and seventeenth centuries became the topic that played a decisive role in historiographical developments.

Kuhn’s influence was incomparably greater in the field of philosophy. Structure was translated into some twenty languages and sold over a million copies. It is still indispensable reading not only in philosophy of science, but also in philosophy generally. More than any other text, it was responsible for the overthrow of logical positivism both as a source of a certain image of science and as a philosophical practice. After Structure, the field of philosophy of science took a historical turn in the 1970s and 1980s, using historical case studies either to ground or to test “empirically” a given view of the development of science.

Kuhn’s views also led to the Strong Programme in the Sociology of Scientific Knowledge founded by Barry Barnes and David Bloor, who argued that the very content and nature of scientific knowledge can be explained sociologically and a fortiori naturalistically. Kuhn, however, distanced himself from the Strong Programme, characterizing it as a “deconstruction that has gone mad.” With its emphasis on the scientific community and its practices, Kuhn’s philosophy eventually gave rise to what is called social studies of science, a subspecialty that attempts to unify philosophical, sociological, anthropological, and ethnographic approaches into a coherent whole. The feminist critique of science, too, that has emerged since the 1980s owes much to Kuhn’s insights. Indeed, all of these studies are now routinely referred to as “post-Kuhnian.”

Kuhn’s views had virtually no impact on the practice of science itself, but they did catch the attention of both physicists and social scientists. While the former group was largely critical, the latter group was mostly sympathetic. The interest of social scientists was to a great extent methodological: they wondered whether sociology, political science, and economics were “mature sciences” like physics and chemistry, governed by a single paradigm at a given period, and whether they conformed to the pattern of normal science–crisis–revolution–normal science. One noticeable effect of such studies was that physical sciences came to be seen as being as interpretive as social sciences were, and in that respect not so different from them.

Were Kuhn’s ideas as revolutionary as they were widely taken to be? Recent historical studies on the origins and development of logical positivism indicate that there are as many similarities and continuities as there are differences and discontinuities between that movement and Kuhn’s views. Kuhn himself confessed later in life that he had fortunately very limited firsthand knowledge of logical positivist writings; otherwise, he said, he would have written a completely different book. But, as Alexander Bird put it, like Copernicus and Planck, Kuhn inaugurated a revolution that went far beyond what he himself imagined.



“Robert Boyle and Structural Chemistry in the Seventeenth Century.” Isis 43 (1952): 12–36.

The Copernican Revolution: Planetary Astronomy in the Development of Western Thought. Cambridge, MA: Harvard University Press, 1957.

“The Function of Dogma in Scientific Research.” In Scientific Change: Historical Studies in the Intellectual, Social and Technical Conditions for Scientific Discovery and Technical Invention, from Antiquity to the Present, edited by Alistair C. Crombie. London: Heinemann, 1963.

With John L. Heilbron, Paul Forman, and Lini Allen. Sources for History of Quantum Physics: An Inventory and Report. Memoirs of the American Philosophical Society, 68. Philadelphia: American Philosophical Society, 1967.

With John L. Heilbron. “The Genesis of the Bohr Atom.” Historical Studies in the Physical Sciences 1 (1969): 211–290.

“Alexandre Koyré and the History of Science: On an Intellectual Revolution.” Encounter 34 (1970): 67–69.

The Structure of Scientific Revolutions. 2nd enlarged ed. Chicago: University of Chicago Press, 1970. First published in 1962. The second edition contains the 1969 “Postscript.”

“Notes on Lakatos.” In PSA 1970: In Memory of Rudolf Carnap; Proceedings of the 1970 Biennial Meeting, Philosophy of Science Association, edited by Roger C. Buck and Robert S. Cohen. Boston Studies in the Philosophy of Science, vol. 8. Dordrecht, Netherlands: D. Reidel, 1971.

The Essential Tension: Selected Studies in Scientific Tradition and Change. Chicago: University of Chicago Press, 1977.

Black-Body Theory and the Quantum Discontinuity, 1894–1912. Oxford: Oxford University Press, 1978. 2nd ed. with a new “Afterword.” Chicago: University of Chicago Press, 1987.

“History of Science.” In Current Research in Philosophy of Science, edited by Peter D. Asquith and Henry E. Kyburg. East Lansing, MI: Philosophy of Science Association, 1979.

“The Halt and the Blind: Philosophy and History of Science.” British Journal for the Philosophy of Science 31 (1980): 181–192.

The Road since Structure: Philosophical Essays, 1970–1993, with an Autobiographical Interview. Edited by James Conant and John Haugeland. Chicago: University of Chicago Press, 2000.


Barnes, Barry. T. S. Kuhn and Social Science. London: Macmillan, 1982.

Bird, Alexander. Thomas Kuhn. Princeton, NJ: Princeton University Press, 2000. A critical overview.

Darrigol, Olivier. “The Historians’ Disagreement over the Meaning of Planck’s Quantum.” Centaurus 43 (2001): 219–239.

Friedman, Michael. “On the Sociology of Scientific Knowledge and Its Philosophical Agenda.” Studies in History and Philosophy of Science 29 (1998): 239–271.

Fuller, Steve. Thomas Kuhn: A Philosophical History for Our Times. Chicago: University of Chicago Press, 2000.

Galison, Peter. “Kuhn and the Quantum Controversy.” British Journal for the Philosophy of Science 32 (1981): 71–85.

Gutting, Gary, ed. Paradigms and Revolutions. Notre Dame, IN: University of Notre Dame Press, 1980. Written by eminent philosophers, social scientists, and historians of science, these essays assess Kuhn’s pre-1980 writings and their impact in various fields.

Horwich, Paul, ed. World Changes: Thomas Kuhn and the Nature of Science. Cambridge, MA: MIT Press, 1993. An in-depth discussion of Kuhn’s latest views; also contains Kuhn’s long reply “Afterwords,” which is his final statement.

Hoyningen-Huene, Paul. Reconstructing Scientific Revolutions: Thomas S. Kuhns Philosophy of Science. Chicago: University of Chicago Press, 1993. Meticulous exposition, with a foreword by Kuhn.

Irzik, Gürol, and Teo Grünberg. “Carnap and Kuhn: Arch Enemies or Close Allies?” British Journal for the Philosophy of Science 46 (1995): 285–307.

Kindi, Vasso. “The Relation of History of Science to Philosophy of Science in The Structure of Scientific Revolutions and Kuhn’s Later Philosophical Work.” Perspectives on Science 13 (2006): 495–530.

Koyré, Alexandre. Études galiléennes. Paris: Hermann, 1939. Also 1966 and 1997. Translation by John Mepham as Galilean Studies. Atlantic Highlands, NJ: Humanities Press, 1978.

Lakatos, Imre, and Alan Musgrave, eds. Criticism and the Growth of Knowledge. London: Cambridge University Press, 1970. An early classic volume displaying the then-current state of debate among Kuhn, Popper, Lakatos, Feyerabend, and others.

Newton-Smith, W. H. The Rationality of Science. Boston: Routledge and Kegan Paul, 1981. A good overview of philosophy of science.

Nickles, Thomas, ed. Thomas Kuhn. Cambridge, U.K.: Cambridge University Press, 2003.

Sankey, Howard. Rationality, Relativism and Incommensurability. Aldershot, U.K.: Ashgate, 1997.

Sharrock, Wes, and Rupert Read. Kuhn: Philosopher of Scientific Revolutions. Cambridge, U.K.: Polity Press, 2002.

Westman, Robert S. “Two Cultures or One?: A Second Look at Kuhn’s The Copernican Revolution.” Isis 85 (1994): 79–115.

Gürol Irzik

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Thomas Samuel Kuhn

Thomas Samuel Kuhn

Thomas Samuel Kuhn (1922-1996) was an American historian and philosopher of science. He found that basic ideas about how nature should be studied were dogmatically accepted in normal science, increasingly questioned, and overthrown during scientific revolutions.

Born in Cincinnati, Ohio, in 1922, Thomas Kuhn was trained as a physicist but became an educator after receiving his Ph.D. in physics from Harvard in 1949. He taught as an assistant professor of the history of science at Harvard from 1952 to 1957, as a professor of the history of science at Berkeley (California) from 1958 to 1964, as a professor of the history of science at Princeton from 1964 to 1979, as a professor of philosophy and the history of science at Massachusetts Institute of Technology (MIT) from 1979 to 1983, and finally, Laurence Rockefeller professor of philosophy at MIT from 1983 to 1991. A member of many professional organizations, he was president of the History of Science Society from 1968 to 1970. He received the Howard T. Behrman award at Princeton in 1977 and the George Sarton medal from the History of Science Society in 1982.

Kuhn's scholarly achievements were many. He held positions as a Lowell lecturer in 1951, Guggenheim fellow from 1954 to 1955, fellow of the Center for Advanced Studies in Behavioral Science from 1958 to 1959, director of the Sources for the History of Quantum Physics Project from 1961 to 1964, director of the Social Science Research Council from 1964 to 1967, director of the program for history and philosophy of science at Princeton from 1967 to 1972, member of the Institute for Advanced Study at Princeton from 1972 to 1979, and member of the Assembly for Behavioral and Social Science in 1980.

Kuhn was best known for debunking the common belief that science develops by the accumulation of individual discoveries. In the summer of 1947 something happened that shattered the image of science he had received as a physicist. He was asked to interrupt his doctorate physics project to lecture on the origins of Newton's physics. Predecessors of Newton such as Galileo and Descartes were raised within the Aristotelian scientific tradition. Kuhn was shocked to find in Aristotle's physics precious little a Newtonian could agree with or even make sense of. He asked himself how Aristotle, so brilliant on other topics, could be so confused about motion and why his views on motion were taken so seriously by later generations. One hot summer day while reading Aristotle, Kuhn said he he had a brainstorm. "I gazed abstractly out the window of my room. Suddenly the fragments in my head sorted themselves out in a new way, and fell into place together, my jaw dropped," as reported by his friend and admirer, Malcolm Gladwell, in the July 8th issue of The New Yorker. He realized that he had been misreading Aristotle by assuming a Newtonian point of view. Taught that science progresses cumulatively, he had sought to find what Aristotle contributed to Newton's mechanics. This effort was wrong-headed, because the two men had basically different ways of approaching the study of motion.

For example, Aristotle's interest in change in general led him to regard motion as a change of state, whereas Newton's interest in elementary particles, thought to be in continuous motion, led him to regard motion as a state. That continuous motion requires explanation by appeal to some force keeping it in motion was taken as obvious by Aristotle. But Newton thought that continued motion at a certain speed needed no explanation in terms of forces. Newton invoked the gravitational force to explain acceleration and advanced a law that an object in motion remains in motion unless acted upon by an external force.

This discovery turned Kuhn's interest from physics to the history of physics and eventually to the bearing of the history of science on philosophy of science. His working hypothesis that reading a historical text requires sensitivity to changes in meaning provided new insight into the work of such great physicists as Boyle, Lavoisier, Dalton, Boltzmann, and Plank. This hypothesis was a generalization of his finding that Aristotle and Newton worked on different research projects with different starting points which eventuated in different meanings for basic terms such as "motion" or "force." Most people probably think that science has exhibited a steady accumulation of knowledge. But Kuhn's study of the history of physics showed this belief to be false for the simple reason that different research traditions have different basic views that are in conflict. Scientists of historically successive traditions differ about what phenomena ought to be included in their studies, about the nature of the phenomena about what aspects of the phenomena do or do not need explanation, and even about what counts as a good explanation or a plausible hypothesis or a rigorous test of theory.

Especially striking to Kuhn was the fact that scientists rarely argued explicitly about these basic research decisions. Scientific theories were popularly viewed as based entirely on inferences from observational evidence. But no amount of experimental testing can dictate these decisions because they are logically prior to testing by their nature. What, if not observations, explains the consensus of a community of scientists within the same tradition at a given time? Kuhn boldly conjectured that they must share common commitments, not based on observation or logic alone, in which these matters are implicitly settled. Most scientific practice is a complex mopping-up operation, based on group commitments, which extends the implications of the most recent theoretical breakthrough. Here, at last, was the concept for which Kuhn had been searching: the concept of normal science taking for granted a paradigm, the locus of shared commitments.

In 1962 Kuhn published his landmark book on scientific revolutions, which was eventually translated into 16 languages and sold over a million copies. He coined the term "paradigm" to refer to accepted achievements such as Newton's Principia which contain examples of good scientific practice. These examples include law, theory, application, and instrumentation. They function as models for further work. The result is a coherent research tradition. In his postscript to the second edition, Kuhn pointed out the two senses of "paradigm" used in his book. In the narrow sense, it is one or more achievement wherein scientists find examples of the kind of work they wish to emulate, called "exemplars." In the broad sense it is the shared body of preconceptions controlling the expectations of scientists, called a "disciplinary matrix." Persistent use of exemplars as models gives rise to a disciplinary matrix that determines the problems selected for study and the sorts of answers acceptable to the scientific community.

Using the paradigm concept, Kuhn developed a theory of scientific change. A tradition is pre-scientific if it has no paradigm. A scientific tradition typically passes through a sequence of normal science-crisis-revolution-new normal science. Normal science is puzzle-solving governed by a paradigm accepted uncritically. Difficulties are brushed aside and blamed on the failure of the scientist to extend the paradigm properly. A crisis begins when scientists view these difficulties as stemming from their paradigm, not themselves. If the crisis is not resolved, a revolution sets in, but the old paradigm is not given up until it can be replaced by a new one. Then new normal science begins and the cycle is repeated. Just when to accept a new paradigm and when to stick to the old one is a matter not subject to proof, although good reasons can be adduced for both options. Scientific rationality is not found in rules of scientific method but in the collective judgment of the scientific community. We must give up the notion that science progresses cumulatively toward the truth about reality; after a revolution it merely replaces one way of seeing the world with another.

Kuhn's theory of scientific change was the most widely influential philosophy of science since that of his mentor, Sir Karl Popper. Kuhn's claims were much discussed by scientists, who generally accepted them; by sociologists, who took them to elucidate the subculture of scientists; by historians, who found cases of scientific change not fitting his model; and by philosophers, who generally abhorred Kuhn's historical relativism about knowledge but accepted the need for their theories of science to do justice to its history. Kuhn was often perturbed by those who sought to— in his view—apply his ideas to areas where it was inappropriate. "I'm much fonder of my critics than my fans," he often said, according to Gladwell's New Yorker article. Indeed, he even tried in later years to replace the term "paradigm"—which he felt was being overused—with "exemplar." Kuhn died June 17, 1996, at his home in Cambridge, Massachusetts. Notwithstanding the tendency of some to misapply his theories, history will show that Kuhn indeed transformed the image of science by making it exciting and emphasizing that it is a social process in addition to being a rational one.

Further Reading

Kuhn's four books are The Copernican Revolution (1957), The Essential Tension (1959), The Structure of Scientific Revolutions (1962, second edition 1970), and Black-Body Theory and the Quantum Discontinuity 1894-1912 (1978). Clear discussions of his views in order of increasing sophistication are found in George Kneller's Science as a Human Endeavor (1978), Garry Gutting's Paradigms and Revolutions (1980), Harold Brown's Perception, Theory and Commitment (1977), and Ian Hacking's Scientific Revolutions (1981). "My Jaw Dropped," by Malcolm Gladwell in the July 8th issue of The New Yorker is a tribute by an admirer. His obituary, by Lawrence Van Gelder, is in the June 29th edition of The New York Times.

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Kuhn, Thomas Samuel

Thomas Samuel Kuhn, 1922–96, American philosopher and historian of science, b. Cincinnati, Ohio. He trained as a physicist at Harvard (Ph.D. 1949), where he taught the history of science from 1948 to 1956. He subsequently taught at the Univ. of California, Berkeley (until 1964), Princeton (until 1979), and the Massachusetts Institute of Technology (until 1991). In his highly influential work The Structure of Scientific Revolutions (1962), Kuhn distinguished between normal science and revolutionary science. In normal science, researchers operating within a particular "paradigm," i.e., Ptolemaic astronomy, engage in activity that involves solving problems related to the paradigm. In revolutionary science, which occurs rarely, researchers abandon one paradigm, i.e. Ptolemaic astronomy, and embrace another, i.e., Copernican astronomy. Kuhn held the abandoned paradigm and the embraced one to be "incommensurable" with one another such that the fundamental concepts of one cannot be rendered by the terms of the other. The jump from one paradigm to another, he argued, has a sociological explanation, but no strictly rational justification. Kuhn's other works include The Copernican Revolution (1957) and The Essential Tension (1977).

See G. Gutting, ed., Paradigms and Revolutions: Appraisals and Applications of Thomas Kuhn's Philosophy of Science (1980).

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