This book explains the poetics of Philodemus of Gadara, a first-century BCE Epicurean philosopher and poet, whose On Poems survives among the Herculaneum papyri. His main critical principle is that form and content are inseparable and mutually reinforcing: a change in one means a change in the other. The poet uses this marriage of form and content to create a hard-to-pin-down psychological effect in the audience. Poems produce “additional thoughts” in the audience, and these entertain them. It seems clear that Philodemus expected good poets to arrange form and content suggestively, so that the poems could exert a lasting pull on the minds of the audience. Additionally, the book summarizes the views of Philodemus’ opponents, the terminology of Hellenistic literary criticism, and the history of the Garden’s engagement with poetics. Epicurus did not write an On Poems but Metrodorus did, and this is probably Philodemus’ touchstone for his own views. The book concludes with an appendix of topics that Philodemus handles but which do not fit neatly into another chapter. I discuss his views on genre, mimesis, “appropriateness,” utility, and various technical terms.