SOURCE: “Books of The Times,” in The New York Times, April 20, 1979, p. C29.

In the following review of Concepts and Categories, Leonard traces the development of Berlin's thought, interests, and literary style from the 1930s through the 1960s.

They must have had fun—Isaiah Berlin and Stuart Hampshire and A. J. Ayer—lolling around Oxford in the late 1930's, wrangling over positivism and symbolic logic, verification and phenomenalism, wondering about linguistics. And it must have been more of an emotional wrench than Mr. Berlin, now Sir Isaiah, is willing to concede in his brief preface to this book, when he decided at the end of the war to look in another direction:

“I asked myself whether I wished to devote the rest of my life to a study, however fascinating and important in itself, which, transforming as its achievements undoubtedly were, would not, any more than criticism or...