Of all the writings on theory and aestheticsancient, medieval, or modernthe most important is indisputably Aristotles Poetics, the first philosophical treatise to propound a theory of literature. In the Poetics, Aristotle writes that he will speak of comedybut there is no further mention of comedy. Aristotle writes also that he will address catharsis and an analysis of what is funny. But he does not actually address any of those ideas. The surviving Poetics is incomplete.Until today. Here, Walter Watson offers a new interpretation of the lost second book of Aristotle's Poetics. Based on Richard Jankos philological reconstruction of the epitome, a summary first recovered in 1839 and hotly contested thereafter, Watson mounts a compelling philosophical argument that places the statements of this summary of the Aristotelian text in their true context. Watson renders lucid and complete explanations of Aristotles ideas about catharsis, comedy, and a summary account of the different types of poetry, ideas that influenced not only Ciceros theory of the ridiculous, but also Freuds theory of jokes, humor, and the comic.Finally, more than two millennia after it was first written, and after five hundred years of scrutiny, Aristotles Poetics is more complete than ever before. Here, at last, Aristotles lost second book is found again.