Aristotle inaugurated the systematic study of comedy with the lost second book of his poetics, the sequel to his profoundly original and influential work on tragedy. Professor Janko here argues for a close affinity between Poetics II and a manuscript dismissed by nineteenth-century scholars as a near forgery, the Tractatus Coislinianus. A new edition of the Tractatus is accompanied by facing translation, interpretive essays, a full reconstruction of Poetics II, and commentary.