Bob Bielk · Public domain

Argued in The Structure of Scientific Revolutions (1962) that science doesn't progress smoothly but lurches between settled frameworks through periodic "paradigm shifts" — a phrase so useful it escaped academia entirely and became ordinary English. He contended that what counts as scientific truth at a given moment can't be settled by objective criteria alone, since competing paradigms are often incommensurable with one another. The book remains one of the most cited works in twentieth-century philosophy of science.