- Befitting its subject, this study of jokes is neither deep nor systematic, but light, funny, and thought-provoking. As one suspicious of theories, Cohen (Philosophy/Univ. of Chicago) offers ``no comprehensive theory of jokes,'' contenting himself instead with relatively disconnected remarks about how some jokes work and ``what their existence may show about those of us who love them.'' This lack of philosophical ambition is frustrating at times, with some observations trite (e.g., that we joke about death to gain power over it) or insufficiently explored (the promising but stunted section on how one creates a joke). Yet the method fits the material, allowing the author to pepper the book with a diversity of jokes without flattening their humor as a steamroller theory might. Such a book is only as good as its jokes, and most of his are good. His taste runs to long and detailed (the longest runs three pages) but with punch lines worth the wait: see the one about the New York cab driver whose fare wants to be driven to Chicago. But short jokes are supplied too: ``What's big and gray, and wrote gloomy poetry? T.S. Elephant.'' Most are cerebral, sometimes excessively so: ``Wagner is the Puccini of music'' is funny when you think about it, but ``What's round and purple, and commutes to work? An Abelian grape'' may elude all but mathematicians. Among Cohen's better points: all jokes are conditional, presupposing varying degrees of knowledge in the audience; successful jokes achieve intimacy between teller and hearer; and jokes can seem morally objectionable while also being funny. The most detailed treatment is given to Jewish jokes, which Cohen traces to biblical and talmudic roots and characterizes as outsiders' humor rife with ``crazy logic.'' It's not Aristotle's lost book on comedy, but it does combine entertainment and ideas in the gossamer package.