Alfred Jules Ayer's life is at least as interesting as his philosophy. In challenging metaphysics' claim to essential truths about the universe and human morality, Ayer defined philosophy as a second-order discipline devoted to understanding the meaning of critical concepts, such as causation and the mind. In classic works, such as Language, Truth and Logic, and studies of such philosophers as Wittgenstein and Russell, Ayer demonstrated the range and role of his logical positivist approach. But Ayer separated philosophy from life partly because of his own hedonistic appreciation for life: he had affairs with several women at a time; socialized with intellectuals, show-business folk, and society types, on both sides of the Atlantic; and was a frequent television guest and a fanatical football fan. Drawing on interviews as well as other sources, Rogers fills in some of the interesting gaps left by Ayer's two volumes of autobiography. \plain\f0\fs17 Mary Carroll 　　"Freddie" Ayer (1910-1989) "was like an eighteenth-century rationalist voluptuary," one of his former students once recalled. Oxford historian of philosophy Rogers (Pascal: In Praise of Vanity) captures both aspects of the notable philosopher who believed in a life well livedDand asked that the song "Oh, What a Beautiful Doll" be played at his funeralDbut the frenetic voluptuary is much more vivid (Rogers identifies 30 of Ayer's mistresses, almost all by name, including gossip columnist Sheilah Graham) than the exponent of reason. Ayer came from wealthy families on both sides, went to the best schools and knew the beautiful and best-connected people. Precociously clever and narcissistically bent, he was "remote," Rogers concedes, "from some of the more ordinary human emotions." Yet his Language, Truth and Logic, published when he was only 25, achieved cult status among English intellectuals who admired his militant empiricism and rejection of what he saw as fashionable cant. His books were often as audacious as his womanizing, and identified nonsense where others perceived truth (Ayer maintained that philosophy "cannot discover anything about the world; only empirical science can do that"). He gained a gadfly reputation for his brilliance as a precise and accessible talker and writer. Rogers skillfully evokes Ayer's personality and life but finds it much more difficult to explain him as a philosopher with a lasting message. The publisher quotes Alain de Botton's praise for this biography in England's Sunday Mail and it may garner fine reviews here as well, but despite the raciness of Ayer's life, the primary audience for this volume will be found only among serious students of 20th-century philosophy. Illus. not seen by PW. Agent, Kris Dahl, ICM. (Oct. 20)