Attempting to comprehend the meaning of the two central themes of the dialogue—virtue and knowledge—directs the reader to pay close attention to the form of the dialogue. Hoping to have thematic questions answered thematically by Socrates is to hope in vain. To uncover what Plato is really up to, the reader must look for answers in the method, not the matter, of the argument. In this sense, Canadian philosopher's Marshall McLuhan's famous dictum, "the medium is the message," needs to be taken very seriously when reading a Platonic dialogue.

For Plato, the best method of discovering truth is the dialectic (in Greek, elenchus), the kind of question and answer format favored by Socrates. Not incidentally, the dialectic is in fact a theme of Protagoras, and Socrates makes a number of arguments to demonstrate that it is indeed the best way to do philosophy. Socrates states that the dialectic tests both the opinions under review and the people who express those opinions; thus, it deals with abstract argument at the same time that it grounds that abstraction in real figures. Plato's dialogues do much the same thing; in the same moment that they treat difficult questions of great philosophical importance, they are also dramatic texts representing real people. This ability to represent psychological conflict and abstruse reasoning simultaneously is as much a feature of the dialectic as the back-and-forth motion set up by the frequent questions.

But the dialectic is not merely internal to the text, something represented by the words on the page. This internal mechanism is part of the dialectical process initiated by Plato, but that process continues beyond those words. Reading the text, we too enter into a dialectic—a process of question and answer—with the characters having the conversation, with the theories being expounded, and also with the form in which those characters and theories are represented. One of the results of this is that, in reading Plato, we too are being tested, as much as we wish to test the text. Another result is that any interpretation cannot be taken as final. Each interpretation is merely a starting point for another series of questioning. As Socrates states at the end of Protagoras, everything has to be thought through once again, from the very beginning.