Zina Giannopoulou argues that Theaetetus is a philosophically sophisticated elaboration of Apology that successfully differentiates Socrates from the sophists. In Apology Socrates defends his philosophical activity partly by distinguishing it from sophistic practices, and in Theaetetus he enacts this distinction: the self-proclaimed ignorant and pious Socrates of Apology poses as the barren practitioner of midwifery, an art that enjoys divine support, and helps his pregnant interlocutor to engender his ideas. Whereas sophistic expertise fills others' souls with items of dubious epistemic quality, Socratic midwifery removes, tests, and discards falsities. In Theaetetus Plato drapes the Socrates of Apology with obstetric garb and stages a philosophical contest between him and the seemingly wise men with whose definitions Theaetetus' soul teems, chief among whom is Protagoras. By proving the indefensibility of these definitions, Socrates challenges their authors' wisdom.