Introduction

The Theaetetus is almost alone among Plato’s dialogues in being fairly precisely datable. In the “preface” which precedes the dialogue proper Theaetetus is said to have just been brought back from battle near Corinth, wounded and suffering from dysentery; it seems clear that he is about to die. Euclides, who reports these facts to Terpsion, is reminded of a conversation Socrates once had with Theaetetus when he was quite a young man, not long before Socrates’ death. On this occasion Socrates was much impressed with Theaetetus’ mental powers, and predicted for him the illustrious future he in fact turned out to have. It is this conversation which the main dialogue records. The tributes to Theaetetus’ prowess in the preface and in the dialogue proper, where one of his main mathematical achievements is described and celebrated (147d–148b), strongly suggest that Plato composed the dialogue as a memorial to him. If so, the date of composition must fall not long after the battle in which Theaetetus was fatally wounded. Now there were only two battles of Corinth during Plato’s lifetime, one in 394 and one in 369, ¹ and the earlier date, though it has had some supporters, notable among them Lewis Campbell, ² is hardly acceptable if the dialogue was composed shortly after Theaetetus’ death, and has not generally been adopted by scholars. The Theaetetus, then, seems fairly firmly assignable to the early 360’s.