Thomas Kuhn

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Thomas Samuel Kuhn (July 18, 1922June 17, 1996) was an American physicist, historian, and philosopher of science and who wrote extensively on the history of science and developed several important notions in the philosophy of science.


  • Only when they must choose between competing theories do scientists behave like philosophers.
    • Kuhn (1970) in Logic of Discovery or Psychology of Research?, edited by Imre Lakatos, Alan Musgrave (1970). Criticism and the growth of knowledge. Cambridge University Press. p. 7. ISBN 0521096235. 

The Structure of Scientific Revolutions (1962)[edit]

Thomas Kuhn. The Structure of Scientific Revolutions. University of Chicago Press, 1962; second edition, enlarged, 1970; third edition 1996; fourth edition 2012.

  • To my complete surprise, that exposure to out-of-date scientific theory and practice radically undermined some of my basic conceptions about the nature of science and the reasons for its special success.
    Those conceptions were ones I had previously drawn partly from scientific training itself and partly from a long-standing avocational interest in the philosophy of science. Somehow, whatever their pedagogic utility and their abstract plausibility, those notions did not at all fit the enterprise that historical study displayed. Yet they were and are fundamental to many discussions of science, and their failures of verisimilitude therefore seemed thoroughly worth pursuing. The result was a drastic shift in my career plans, a shift from physics to history of science and then, gradually, from relatively straightforward historical problems back to the more philosophical concerns that had initially led me to history.
    • Preface
  • Somehow, the practice of astronomy, physics, chemistry or biology normally fails to evoke the controversies over fundamentals that today seem endemic among, say, psychologists or sociologists. Attempting to discover the source of that difference led me to recognize the role in scientific research of what I have since called “paradigms.” These I take to be universally recognized scientific achievements that for a time provide model problems and solutions for a community of practitioners.
    • p. xiii (2012 ed.); Preface
  • 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.
    • I. Introduction: A Role of History
  • 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.
    • I. Introduction: A Role of History
  • Normal science, the activity in which most scientists inevitably spend most all their time, is predicated on the assumption that the scientific community knows what the world is like. Normal science often suppresses fundamental novelties because they are necessarily subversive of its basic commitments.
    • p. 5; I. Introduction: A Role of History
  • "Normal science" means research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for its further practice
    • p. 10; II. The Route to Normal Science
  • Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice. That commitment and the apparent consensus it produces are prerequisites for normal science, i.e., for the genesis and continuation of a particular research tradition.
    • p. 11 (2012 ed.)
  • Ever since prehistoric antiquity one field of study after another has crossed the divide between what the historian might call its prehistory as a science and its history proper. These transitions to maturity have seldom been so sudden or so unequivocal as my necessarily schematic discussion may have implied. But neither have they been historically gradual, coextensive, that is to say, with the entire development of the fields within which they occurred.
    • p. 22 (2012 ed.); II. The Route to Normal Science
  • Few people who are not actually practitioners of a mature science realize how much mop-up work of this sort a paradigm leaves to be done or quite how fascinating such work can prove in the execution.
    • p. 24 (2012 ed.); III. The Nature of Normal Science
  • These three classes of problems—determination of significant fact, matching of facts with theory, and articulation of theory—exhaust, I think, the literature of normal science, both empirical and theoretical. They do not, of course, quite exhaust the entire literature of science. There are also extraordinary problems, and it may well be their resolution that makes the scientific enterprise as a whole so particularly worthwhile. But extraordinary problems are not to be had for the asking. They emerge only on special occasions prepared by the advance of normal research.
    • p. 34 (2012 ed.); III. The Nature of Normal Science
  • The scientific enterprise as a whole does from time to time prove useful, open up new territory, display order, and test long-accepted belief. Nevertheless, the individual engaged on a normal research problem is almost never doing any one of these things. Once engaged, his motivation is of a rather different sort. What then challenges him is the conviction that, if only he is skillful enough, he will succeed in solving a puzzle that no one before has solved or solved so well.
    • p. 38.
  • Scientists work from models acquired through education and through subsequent exposure to the literature often without quite knowing or needing to know what characteristics have given these models the status of community paradigms
    • p. 46; V. The Priority of Paradigms
  • Normal science, the puzzle-solving activity we have just examined, is a highly cumulative enterprise, eminently successful in its aim, the steady extension of the scope and precision of scientific knowledge. In all these respects it fits with great precision the most usual image of scientific work. Yet one standard product of the scientific enterprise is missing. Normal science does not aim at novelties of fact or theory and, when successful, finds none.
    • p. 52: VI. Anomaly and the Emergence of Scientific Discoveries
  • We must now ask how changes of this sort can come about, considering first discoveries, or novelties of fact, and then inventions, or novelties of theory. That distinction between discovery and invention or between fact and theory will, however, immediately prove to be exceedingly artificial.
    • p. 52 (2012 ed.); VI. Anomaly and the Emergence of Scientific Discoveries
  • In science, as in the playing card experiment, novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation.
    • p. 64 (2012 ed.); VI. Anomaly and the Emergence of Scientific Discoveries
  • In the development of any science, the first received paradigm is usually felt to account quite successfully for most of the observations and experiments easily accessible to that science’s practitioners. Further development, therefore, ordinarily calls for the construction of elaborate equipment, the development of an esoteric vocabulary and skills, and a refinement of concepts that increasingly lessens their resemblance to their usual common-sense prototypes. That professionalization leads, on the one hand, to an immense restriction of the scientist’s vision and to a considerable resistance to paradigm change. The science has become increasingly rigid. On the other hand, within those areas to which the paradigm directs the attention of the group, normal science leads to a detail of information and to a precision of the observation-theory match that could be achieved in no other way.
    • p. 64 (2012 ed.); VI. Anomaly and the Emergence of Scientific Discoveries
  • Philosophers of science have repeatedly demonstrated that more than one theoretical construction can always be placed upon a given collection of data. History of science indicates that, particularly in the early developmental stages of a new paradigm, it is not even very difficult to invent such alternates. But that invention of alternates is just what scientists seldom undertake except during the pre-paradigm stage of their science’s development and at very special occasions during its subsequent evolution. So long as the tools a paradigm supplies continue to prove capable of solving the problems it defines, science moves fastest and penetrates most deeply through confident employment of those tools. The reason is clear. As in manufacture so in science—retooling is an extravagance to be reserved for the occasion that demands it. The significance of crises is the indication they provide that an occasion for retooling has arrived.
    • p. 76 (2012 ed.) ; VII. Crisis and the Emergence of Scientific Theories
  • 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.
    • p. 91 (2012 ed.)
The subject of a gestalt demonstration knows that his perception has shifted because he can make it shift back and forth repeatedly while he holds the same book or piece of paper in his hands...
  • The subject of a gestalt demonstration knows that his perception has shifted because he can make it shift back and forth repeatedly while he holds the same book or piece of paper in his hands. Aware that nothing in his environment has changed, he directs his attention increasingly not to the figure (duck or rabbit) but to the lines of the paper he is looking at. Ultimately he may even learn to see those lines without seeing either of the figures, and he may then say (what he could not legitimately have said earlier) that it is these lines that he really sees but that he sees them alternately as a duck and as a rabbit. ...As in all similar psychological experiments, the effectiveness of the demonstration depends upon its being analyzable in this way. Unless there were an external standard with respect to which a switch of vision could be demonstrated, no conclusion about alternate perceptual possibilities could be drawn.
    • p. 114 (3rd edn.); X. Revolutions as Changes of World View
  • These examples point to the third and most fundamental aspect of the incommensurability of competing paradigms. In a sense that I am unable to explicate further, the proponents of competing paradigms practice their trades in different worlds. One contains constrained bodies that fall slowly, the other pendulums that repeat their motions again and again. In one, solutions are compounds, in the other mixtures. One is embedded in a flat, the other in a curved, matrix of space. Practicing in different worlds, the two groups of scientists see different things when they look from the same point in the same direction. Again, that is not to say that they can see anything they please. Both are looking at the world, and what they look at has not changed. But in some areas they see different things, and they see them in different relations one to the other. That is why a law that cannot even be demonstrated to one group of scientists may occasionally seem intuitively obvious to another.
    • p. 149 XII. The Resolution of Revolutions
  • We may, to be more precise, have to relinquish the notion, explicit or implicit, that changes of paradigm carry scientists and those who learn from them closer and closer to the truth
    • p. 170 XIII. Progress Through Revolutions

The Road Since Structure, 2002[edit]

Thomas Kuhn, The Road since Structure: Philosophical Essays, 1970-1993, with an Autobiographical Interview, Edited by James F. Conant and John Haugeland, University of Chicago Press, 2002

  • I rapidly discovered that Aristotle had known almost no mechanics at all. ... How could his characteristic talents have deserted him so systematically when he turned to the study of motion and mechanics? Equally, if his talents had so deserted him, why had his writings in physics been taken so seriously for so many centuries after his death? ... I was sitting at my desk with the text of Aristotle's Physics open in front of me... Suddenly the fragments in my head sorted themselves out in a new way, and fell into place together. My jaw dropped, for all at once Aristotle seemed a very good physicist indeed, but of a sort I'd never dreamed possible. Now I could understand why he had said what he'd said, and what his authority had been. Statements that had previously seemed egregious mistakes, now seemed at worst near misses within a powerful and generally successful tradition. That sort of experience -- the pieces suddenly sorting themselves out and coming together in a new way -- is the first general characteristic of revolutionary change that I shall be singling out after further consideration of examples. Though scientific revolutions leave much piecemeal mopping up to do, the central change cannot be experienced piecemenal, one step at a time. Instead, it involves some relatively sudden and unstructured transformation in which some part of the flux of experience sorts itself out differently and displays patterns that were not visible before.
    • p. 16-17; from "What Are Scientific Revolutions?" (1982)
  • By now it may be clear that the position I'm developing is a sort of post-Darwinian Kantianism.
    • p. 104; from "The Road since Structure" (1990)

Quotes about Thomas Kuhn[edit]

  • A few years ago I happened to meet Kuhn at a scientific meeting and complained to him about the nonsense that had been attached to his name. He reacted angrily. In a voice loud enough to be heard by everyone in the hall, he shouted, "One thing you have to understand. I am not a Kuhnian."
    • Freeman Dyson, The Sun, The Genome, and The Internet: Tools of Scientific Revolutions (1999)
  • Kuhn cannot take seriously that “there is some one full, objective, true account of nature.” Does this mean that he does not take truth seriously? Not at all. [...]
    Kuhn did reject a simple “correspondence theory” which says true statements correspond to facts about the world.[...]
    In the wave of skepticism that swept American scholarship at the end of the twentieth century, many influential intellectuals took Kuhn as an ally in their denials of truth as a virtue. I mean the thinkers of the sort that cannot write down or utter the word true except by literally or figuratively putting quotation marks around it—to indicate how they shudder at the very thought of so harmful a notion. Many reflective scientists, who admire much of what Kuhn says about the sciences, believe he encouraged deniers.
    It is true that Structure gave enormous impetus to sociological studies of science. Some of that work, with its emphasis on the idea that facts are “socially constructed” and apparent participation in the denial of “truth,” is exactly what conservative scientists protest against. Kuhn made plain that he himself detested that development of his work...
    • Ian Hacking (2012), Introductory Essay, in 50th anniversary edition of Thomas Kuhn's The Structure of Scientific Revolution
  • Notice that there is no sociology in the book. Scientific communities and their practices are, however, at its core, entering with paradigms, as we saw, at page 10 and continuing to the final page of the book. There had been sociology of scientific knowledge before Kuhn, but after Structure it burgeoned, leading to what is now called science studies. This is a self-generating field (with, of course, its own journals and societies) that includes some work in the history and the philosophy of sciences and technology, but whose emphasis is on sociological approaches of various kinds, some observational, some theoretical. Much, and perhaps most, of the really original thinking about the sciences after Kuhn has had a sociological bent.
    Kuhn was hostile to these developments. In the opinion of many younger workers, that is regrettable. Let us put it down to dissatisfaction with growing pains of the field, rather than venturing into tedious metaphors about fathers and sons. One of Kuhn’s marvelous legacies is science studies as we know it today.
    • Ian Hacking (2012), Introductory Essay, in 50th anniversary edition of Thomas Kuhn's The Structure of Scientific Revolution
  • Well, he wasn't a relativist. There's a long and complicated story of the rise of a desire for scientific relativism. Part of it may well be simply sort of rage against reason, the fear of the sciences and a kind of total dislike of the arrogance of a great many scientists who say we're finding out the truth about everything—and here [with Kuhn] there was a way to undermine that arrogance.
    • Ian Hacking, in Gary Stix, "A Q&A with Ian Hacking on Thomas Kuhn's Legacy as "The Paradigm Shift" Turns 50" (April 27, 2012)
  • Kuhn had the genius to find the words and sketch the concepts that made important old philosophical problems relevant to the public and newly discussable by philosophers. He had the strength of mind and commitment to lead the discussion. He could speak the truly incommensurable languages of physics, philosophy, and history, all necessary to frame and advance his epistemological quest. He wrote, as one of his admirers, Margaret Masterman, put it, in a "quasi-poetic style," sometimes veiled, sometimes with "rhetorical exaggeration," but always after careful and even painful thought. Or, to switch metaphors, he drew the portrait of science in the manner of the Impressionists. At a distance, where most viewers stand, the portrait appears illuminating, persuasive, and inspiring; close in, where historians and philosophers stare, it looks sketchy, puzzling, and richly challenging.
  • Kuhn's recognition that science might cease—leaving us with what Charles Sanders Peirce had defined as the "truth" about nature—made it even more imperative for Kuhn than for Popper to challenge science's authority, to deny that science can ever arrive at absolute truth. "The one thing I think you shouldn't say is that now we've found out what the world is really like," Kuhn said. "Because that's not what I think the game is about."
    • John Horgan, The End of Science (1996), Ch. 2 : The End of Philosophy
  • What truth is not, according to Kuhn, is an accurate representation of the world as it is in itself. Scientific theories represent a world, but one partially constituted by the cognitive activities of the scientists themselves. This is not a commonsensical view, but it has a distinguished philosophical pedigree, associated most strongly with Kant. The Kantian view is that the truths we can know are truths about a ‘phenomenal’ world that is the joint product of the ‘things in themselves’ and the organising, conceptual activity of the human mind.
    Kuhn, however, is Kant on wheels. Where Kant held that the human contribution to the phenomenal world is invariant, Kuhn’s view is that it changes fundamentally across a scientific revolution. This is what he means by his notorious statement that, after a scientific revolution, ‘the world changes’. This is neither the trivial claim that scientists’ beliefs about the world change, nor the crazy claim that scientists can change the things in themselves simply by changing their beliefs. It is the claim that the phenomenal world changes because the human contribution to it changes.
    • Peter Lipton, "Kant on Wheels", London Review of Books (19 July 2001)
  • Kuhn as does Popper rejects the idea that science grows by accumulation of eternal truths.. But while according to Popper science is ‘revolution in permanence’, and criticism the heart of the scientific enterprise, according to Kuhn revolution is exceptional and, indeed, extra-scientific, and criticism is, in ‘normal’ times, anathema... The clash between Popper and Kuhn is not about a mere technical point in epistemology. It concerns our central intellectual values, and has implications not only for theoretical physics but also for the underdeveloped social sciences and even for moral and political philosophy. If even in science there is no other way of judging a theory but by assessing the number, faith and vocal energy of its supporters, then this must be even more so in the social sciences: truth lies in power. Thus Kuhn’s position would vindicate, no doubt, unintentionally, the basic political credo of contemporary religious maniacs (‘student revolutionaries’).
  • Kuhn's description of how scientific revolutions happen does not apply to any biological revolution. To be very frank, I cannot understand how this book could have been such a success. The general thesis was not new, and when he did assert specific claims he was almost always wrong!
    • Ernst Mayr, "The Grand old Man of Evolution: An interview with evolutionary biologist Ernst Mayr," Interview by Michael Shermer and Frank J. Sulloway, Skeptic 8 (January 2000)
  • Up until the publication of Thomas Kuhn's The Structure of Scientific Revolutions in 1962, the history, philosophy, and sociology of science maintained an internalist approach to scientific knowledge claims. Science was seen as somehow above any social, political, or cultural influences, and therefore, the examinations of scientific knowledge focused on areas such as 'discoveries,' 'famous men,' and 'the scientific revolution in the West.' When Kuhn opened the door to the possibility that external factors were involved in the development of scientific paradigms, science studies assumed a more critical tone.
    • Diane M. Rodgers (2009) "Debugging the Link Between Social Theory and Social Insects".
  • I’m one of the few physicists I know who likes Thomas Kuhn. He was partly a historian of science, partly a sociologist. He got the basic idea right of what happens when the scientific paradigm shifts. A radical change of perspective suddenly occurs. Wholly new ideas, concepts, abstractions and pictures become relevant. Relativity was a big paradigm shift. Quantum mechanics was a big paradigm shift. So we keep on inventing new realisms. They never completely replace the old ideas, but they do largely replace them with concepts that work better, that describe nature better, that are often very unfamiliar, that make people question what is meant by “reality.” Then the next thing comes along and turns that on its head. And we are always surprised that the old ways of thinking, the wiring that we have or the mathematical wiring that we may have created, simply fail us.
    • Leonard Susskind, in "Bad Boy of Physics", Interview by Peter Byrne, Scientific American (July 2011)
  • [The Structure of Scientific Revolutions] was hugely influential, especially on the liberal arts, giving them ammunition to suggest that science was no better way of knowing the truth than any other way of investigating. It made a huge case of scientists gathering around one truth, and then there’s a tipping point and everyone moves away from that truth to gather around another truth. Hence the title of the book. And this left people with the sense that science is just whatever is in fashion. Kuhn used, as his best example of this, Copernicus. That’s half his book ... almost half of that book describes the Copernican Revolution as an example of the way science works. But that’s not how science works. It’s just not. It’s how things happened until 1600.
  • In his celebrated book The Structure of Scientific Revolutions Thomas Kuhn went a step further and argued that in scientific revolutions the standards (or “paradigms”) by which scientists judge theories change, so that the new theories simply cannot be judged by the prerevolutionary standards. There is much in Kuhn’s book that fits my own experience in science. But in the last chapter Kuhn tentatively attacked the view that science makes progress toward objective truths: “We may, to be more precise, have to relinquish the notion, explicit or implicit, that changes of paradigm carry scientists and those who learn from them closer and closer to the truth.” Kuhn’s book lately seems to have become read (or at least quoted) as a manifesto for a general attack on the presumed objectivity of science.
    • Steven Weinberg, Dreams of a Final Theory (1992), Ch. 7 : Against Philosophy
  • Now, that really was a paradigm shift. For Kuhn it seems to have been the paradigm of paradigm shifts, which set a pattern into which he tried to shoehorn every other scientific revolution. It really does fit Kuhn's description of paradigm shifts: it is extraordinarily difficult for a modern scientist to get into the frame of mind of Aristotelian physics, and Kuhn's statement that all previous views of reality have proved false, though not true of Newtonian mechanics or Maxwellian electrodynamics, certainly does apply to Aristotelian physics.
    Revolutions in science seem to fit Kuhn's description only to the extent that they mark a shift in understanding some aspect of nature from pre-science to modern science. The birth of Newtonian physics was a mega-paradigm shift, but nothing that has happened in our understanding of motion since then—not the transition from Newtonian to Einsteinian mechanics, or from classical to quantum physics—fits Kuhn's description of a paradigm shift.

External links[edit]

Wikipedia has an article about:
  • Thomas Kuhn entry by Alexander Bird in the Stanford Encyclopedia of Philosophy