The art of showing us the truth would have brought our soul into the repose of abiding by the truth, and so would have saved our life.

Socrates's assertion that evil is nothing other than ignorance is one of the most important theories articulated in Protagoras. Here (356d-e), midway through his deconstruction of Protagoras's concept of virtue, he declares that virtue can indeed be taught because it is a form of knowledge. Learning is then of the utmost importance, because it can reform the soul and remold it into a better state. The type of learning required, however, is not that which is taught by Protagoras. Rather, we can overcome ignorance by acquiring the art of measurement, a kind of moral corrective that will allow us to assess accurately the competing merits of various courses of action. For Socrates, such a perspective will ensure that we will always do the right thing, for it will allow us to determine what is right, and it is impossible for us to do wrong while knowing what is right. The art of moral measurement then allows us to penetrate through the deceptions of appearance, and arrive at truth. For Socrates, nothing could be more important, so he concludes that possessing such an art "would have saved our life."