The Structure of Scientific Revolutions

Summary

Thomas Kuhn's essay argues that the sciences do not grow by steady accumulation of facts but pass through long periods of settled work broken by revolutions in which the framework of a field is replaced. It was first published in 1962 by the University of Chicago Press as a monograph in the International Encyclopedia of Unified Science, and a second edition of 1970 added a Postscript answering critics. The book is under copyright, so this library describes it in its own words and gives only two short quotations. Kuhn opens by proposing that the history of science, taken seriously, would change the picture of science found in textbooks. A mature science begins when a community accepts a paradigm: a shared achievement, such as Newton's Principia or Lavoisier's chemistry, that defines legitimate problems and methods. Before that, schools compete, as in early studies of electricity. Normal science then follows, which Kuhn compares to puzzle-solving: scientists extend and refine the paradigm, determine constants and fit nature more closely to it, without seeking fundamental novelty. Anomalies arise, results that resist the paradigm, as in the discovery of oxygen by Priestley and Lavoisier, of X-rays by Roentgen, and of the Leyden jar. Kuhn draws on a psychological experiment by Bruner and Postman with anomalous playing cards to show how expectation shapes perception. When anomalies accumulate, a field enters crisis, as astronomy did before Copernicus, chemistry before Lavoisier, and physics before relativity. Scientists do not abandon a paradigm simply because it faces counterinstances; they abandon it only when another is available. A revolution follows, which Kuhn compares to a political revolution and to a gestalt switch: after it, scientists see the world differently, and the old and new paradigms are in important ways incommensurable, using terms like mass or element in different senses. The choice between paradigms cannot be settled by logic and experiment alone, and Kuhn likens the change of allegiance to a conversion. Textbooks then rewrite history so that revolutions become invisible and the past looks like a line of progress toward the present. In the last section Kuhn asks in what sense science progresses, and answers that it moves away from earlier states rather than toward a fixed goal, much as Darwin's evolution has no goal. The 1969 Postscript distinguishes two senses of paradigm, the disciplinary matrix of a community and the shared exemplars by which students learn, and rejects the charge that his account makes theory choice irrational.

Top Lessons

• Most science is careful puzzle-solving

  Kuhn shows that ordinary scientific work is not a constant challenge to fundamentals but disciplined work within an accepted framework. This normal science is what makes precise measurement and detailed knowledge possible, and it is also what makes anomalies visible.

• Expectation shapes what we notice

  Through the anomalous playing-card experiment and the history of oxygen and X-rays, Kuhn argues that discovery requires recognising that something is wrong with expectation. People trained to see one thing may at first fail to see another.

• How histories are written

  Kuhn argues that textbooks rewrite the past so that earlier scientists seem to have worked on present problems. His claim asks readers to study past thinkers in their own terms rather than as imperfect versions of the present.

• Reasons that persuade without compelling

  Kuhn holds that choosing between paradigms involves good reasons, such as accuracy and fruitfulness, that persuade without forcing assent. Critics charged him with making science irrational; his Postscript replies that values guide choice even where rules cannot dictate it. The debate remains open.

Verified Quotes

Medical Lens

Kuhn's examples come from physics, chemistry and astronomy, not medicine, but the book has a medical root: in the preface he credits Ludwik Fleck, a Polish physician and microbiologist, whose 1935 monograph Genesis and Development of a Scientific Fact traced how the concept of syphilis and the Wassermann reaction were shaped by a medical thought collective. Kuhn's vocabulary of paradigm shift has since been applied widely, and debated, in medicine and psychiatry, for instance to the germ theory of disease or to changes in psychiatric classification; such applications are later uses of his framework rather than claims in the book.

• Preface

  Kuhn acknowledges Fleck's monograph on the history of the concept of syphilis as anticipating many of his own ideas.