A visit by Protagoras to Athens is the dramatic occasion for the conversations depicted in the Protagoras. Protagoras is a celebrity, staying as a guest at the house of Callias, where a large company has gathered. Among the more notable characters present are Critias and Alcibiades, the sophists Prodicus and Hippias, and the two sons of Pericles, Paralus and Xanthippus (314e3–316a5). Socrates is induced to join the gathering by Hippocrates, a young man so eager to meet Protagoras that he has roused Socrates from bed before dawn in the hope of persuading him to use his entrée to secure an audience. Once inside, speaking on behalf of the younger man, Socrates asks Protagoras what Hippocrates could expect to learn should he become his student (318a). The answer – though it is put in various ways – is virtue. And the first sustained discussion is set in train by the doubts Socrates expresses about whether virtue is the kind of thing that can be taught (319a9–320c2).

The so-called great speech is Protagoras' response (320c2–328d2). When it is over, Socrates declares himself convinced that virtue can be taught. He is, however, still troubled by one small question (329b6–d2). This question is the occasion for a new sequence of arguments that occupies the rest of the dialogue apart from a procedural dispute (334c9–338e7) and a substantial digression in which the interpretation of a poem of Simonides is discussed (338e8–349a7).