Thomas S. Kuhn

Thomas Samuel Kuhn was born in Cincinnati in 1922 and trained as a physicist, completing his PhD at Harvard in 1949. He might have remained a physicist, but a course he taught at Harvard on the history of science for non-scientists sent him back to primary sources and forced him to confront an uncomfortable fact: the history of science did not look like what scientists said it looked like. Science was not, in practice, the orderly accumulation of confirmed facts that its popular image suggested. Something more disruptive was happening, and the standard account could not explain it. He spent the next decade writing The Structure of Scientific Revolutions.

Published in 1962 as part of the International Encyclopedia of Unified Science, the book introduced "paradigm" and "paradigm shift" to the English language. It is now one of the most-cited academic texts of the 20th century, cited more heavily in the social sciences and humanities than in the natural sciences — a fact that would have complicated Kuhn's feelings, since he considered himself a philosopher of science and was wary of how his ideas were being appropriated.

The central argument runs as follows: science normally operates within a paradigm — a set of shared assumptions, methods, and exemplary problems that defines what counts as a legitimate scientific question and a valid answer. "Normal science" is the working out of puzzles within the paradigm. Anomalies — results that don't fit — accumulate over time, but scientists initially respond by adjusting auxiliary hypotheses rather than abandoning the paradigm. When anomalies become too numerous or too central to explain away, a crisis develops. A new paradigm is proposed — by a younger scientist, typically, or an outsider to the field. The transition is not a smooth rational process but a conversion: scientists do not gradually become persuaded by evidence; they switch allegiances, often after the old guard has literally died. The new paradigm is "incommensurable" with the old — its basic terms and assumptions are different enough that direct comparison is difficult or impossible.

The philosophical consequences were contested immediately. If paradigms are incommensurable, does that mean there is no truth, only successive paradigms? Is science's claim to progress merely the claim of the currently dominant paradigm about itself? Kuhn spent much of his later career — The Essential Tension (1977), Black-Body Theory and the Quantum Discontinuity (1978), and the unfinished manuscript published posthumously as The Road Since Structure — trying to clarify what he did and did not mean. He was not a relativist, he insisted; paradigm change is not arbitrary; later paradigms solve more problems. But he could never quite stop the constructivist and postmodern readings of his work, which found in it a license he did not intend to grant.

His influence outside philosophy of science has been enormous and uneven. The term "paradigm shift" has been degraded by business consultants until it means nothing more than "significant change." In the humanities and social sciences, Kuhn was read as arguing that scientific knowledge is socially constructed, which fueled the science wars of the 1990s. In organizational theory and business strategy, his framework has been applied — with varying degrees of rigor — to industries, markets, and technologies. The original text, at roughly 170 pages, is precise and careful in ways that the popular reception rarely preserves. It rewards reading in its original form.