1922-1996 -- Thomas S. Kuhn, a historian of science, turned his business upside down with a radical idea of what makes a scientific revolution -- and created one of the foremost cliches of our time.

Weightier than the critical mass, sharper than the cutting edge, bigger even than the quantum leap -- the great intellectual cliche of our age is (ital)paradigm shift(end). This was Thomas S. Kuhn's contribution to our culture, and he was not altogether happy about it.

Kuhn was a physicist turned historian of science, a philosopher of knowledge and, in his spare time (what can we read into this?), an avid rider of roller coasters. His 172-page masterpiece, ''The Structure of Scientific Revolutions,'' published in 1962, arguably became the most influential work of philosophy in the latter half of the 20th century. It sold more than a million copies. It introduced paradigms, new paradigms, pre- and post-paradigms and, of course, paradigm shifts. He once said that he had not bothered with an index because its main entry would be ''paradigm, 1-172, passim.'' ''Unfortunately,'' he said, ''paradigms took on a life of their own.''

If you yourself have used the word without being exactly sure what it means, you are in good company. One of Kuhn's critics (he had many) claimed to have isolated 22 distinct meanings for paradigm in the book, and Kuhn confessed to a certain elasticity in his use of the term. Nonetheless, it is a genuine and powerful notion, its presence in our language well deserved.

Kuhn saw that science does not always make smooth and gradual progress, with researchers calmly adding their bricks to the edifice. Sometimes, science changes by means of revolutions. Its practitioners undergo a transformation of vision, like people who stare at that optical-illusion silhouette of a candlestick until they suddenly see it flip into a pair of human faces. The paradigm shift, in contrast to ''normal science,'' means crisis. It means tearing down an established framework and reassembling the pieces into something quite new.

This is a romantic idea, and practitioners of just about every branch of science now claim paradigm shifts almost yearly. Real paradigm shifts are not as common as all that, but they do occur. When I met Kuhn, a decade ago, I was researching a book on chaos and complexity, the most sweeping transformation of scientific vision in our own time. His words applied perfectly: ''It is rather as if the professional community had been suddenly transported to another planet where familiar objects are seen in a different light and are joined by unfamiliar ones as well.''

Kuhn's approach did not altogether flatter scientists. It implied that their enterprise was not a purely rational search for truth but rather an act of construction bound to social forces and constrained by habits and biases. Deconstructionists have seen Kuhn as an ally. But they have often gone too far, suggesting that Kuhn thought of science as a kind of ''mob psychology,'' arbitrary and detached from what old-fashioned types used to call ''reality.'' It is true that Kuhn tried to understand the mechanics of Aristotle, say, on its own terms rather than as a silly and inferior version of Newton. He sought to appreciate its logic as a world view. ''When reading the works of an important thinker,'' he advised, ''look first for the apparent absurdities in the text and ask yourself how a sensible person could have written them.''

But he did not mean to suggest that Aristotelian mechanics would come in handy for aerospace engineers. Newton does describe nature better than Aristotle, and Einstein better than Newton. Kuhn noted that the crises leading to paradigm shifts often begin with new discoveries, experimental discrepancies that cannot be squeezed into the established framework. New data force scientists to see the world differently -- and afterward the data themselves look different. He held a complicated picture of knowledge building in balance.

So, thanks to Kuhn, we've lived through paradigm shifts in child rearing, sports psychology and stock-market analysis. All too many academics have published essays titled ''Brother, Can You Paradigm?'' When Kuhn died in June, it was inevitable that at least one waggish obituarist would say he had now undergone the ultimate paradigm shift -- himself.

Photo: Thomas S. Kuhn (Bill Price/Time Magazine)