Thomas Kuhn

Thomas Samuel Kuhn was born in Cincinnati in 1922 and trained as a physicist — Harvard undergraduate, Harvard PhD in 1949, with a dissertation on the application of quantum mechanics to solids. He was already drifting toward history of science before he finished the doctorate. James Conant, the chemist who ran Harvard, had recruited him to help teach a general-education course in the history of science to non-scientists, and the experience of trying to explain Aristotelian physics to twentieth-century undergraduates without immediately calling it wrong is the experience out of which the rest of Kuhn's career grew.

The book that made him was The Structure of Scientific Revolutions (1962), published as a slim monograph in the International Encyclopedia of Unified Science, of all places, and largely overlooked by professional philosophers of science at first. Its argument, in outline: scientific work proceeds for long periods within an established framework — a "paradigm" — that defines which problems are worth solving and what counts as a solution. Kuhn called this normal science, and it is not the dramatic theory-testing of philosophical legend but a kind of expert puzzle-solving. Anomalies accumulate; eventually a crisis develops; a new paradigm emerges that solves the anomalies while reshaping the questions; the field is reconstituted around it. The transition is a scientific revolution. Old and new paradigms are "incommensurable" in a sense Kuhn argued about for the rest of his life — they cannot be straightforwardly translated into each other, and the choice between them is not fully reducible to evidence.

The book sold over a million copies. "Paradigm shift" entered the language and went on a long tour of contexts Kuhn had not anticipated — business strategy, self-help, marketing, every soft-science department that wanted to sound rigorous. The earlier Copernican Revolution (1957), a careful historical account of how a sun-centered cosmos became thinkable, is in many ways the better book; almost nobody outside the field has read it.

Kuhn spent the rest of his career — at Berkeley, then Princeton, then MIT — trying to take back what he regarded as the wilder misreadings of Structure. He was not, he insisted, a relativist; he did not think science was just one belief system among others; he did not think paradigm change was irrational; he was not licensing the academic left, or the academic right, or any of the popular movements that adopted his vocabulary. The 1969 postscript to Structure is largely an exercise in damage control. The later work on incommensurability and on what he called "lexical taxonomies" is technical, careful, and read by relatively few people. He died of cancer in 1996, at seventy-three, with a third book on theory change unfinished. The complicated relationship of a serious historian to the slogan his serious history produced is itself worth a paradigm.