What Is Self Knowledge?

Critius says that temperance, or knowledge, is knowledge of knowledge. This leaves socrates more confused than ever. How could there be knowledge that knows knowledge? Plato gives us a nice image for this perplexity. He has socrates say that just as a man who yawns tends to make everyone else around him yawn, so one man's confusion tends to infect others with confusion. The dialogue now becomes an inquiry into the nature and usefulness of knowledge.