If one wants to know what happened in Hellenistic poetic theory, Philodemus' survey of poetic theories in the fifth book of his On Poems is an excellent guide. Even though I the survey is well preserved, it has been neglected. Jensen, who published the first complete edition of On Poems 5 in 1923, did not discuss this part of the text; and it has been treated only briefly by others. This is a pity because, as Philodemus shows, the Hellenistic period was an era of great diversity and innovation in literary theory. Philodemus gives evidence of: (1) a refined and highly systematic critical vocabulary; (2) a new concern with verbal form; (3) a new notion of mimesis; and (4) in general, a great proliferation of theories that present alternatives to those of Plato and Aristotle. Hellenistic literary theorists studied Plato and Aristotle critically; some revised or elaborated their views, whereas others opposed them. Ancient poetic theory did not come to a standstill with Aristotle any more than philosophy did.