 As Book 10 begins, Socrates links the coming treatment with what Book 3 had said about imitation. He also establishes the difference between the passages. What follows will defend Book 3’s banishment of “imitative poetry” in terms that the Republic developed after Book 3. “Now that we have differentiated the soul’s eidê,” the danger of imitation becomes more evident (595a–b). An eidos is a kind, and this phrase “kinds of soul” is most often taken to mean the parts of the soul that Book 4 distinguished (435b–441c). The Republic’s theory of reason, spirit, and desire can enlarge what had been in Book 3 no more than suspicion about the impersonation of ignoble people. The new argument will charge poetry with upsetting the balance among the soul’s parts. (Daniel Mailick contributed to this discussion of the Republic’s psychological theory.)