As with Alcibiades, so with Critias, Socrates emphasizes the need to seek self-knowledge in conversation with another. As Socrates understands it, self-knowledge is not a product of introspection. As knowledge of what makes a human being human, self-knowledge is not at all self-contained or independent. It requires knowledge not only of other human beings but also of the nonhuman things to determine the difference between them and thus what is distinctively human. As knowledge of one's limits, self-knowledge as Socrates understands it entails recognition of one's lack of self-sufficiency and the consequent need to join with others. Self-knowledge as Socrates understands it consists in knowledge of one's ignorance rather than, as Critias claims, knowledge of knowledge.
Catherine H. Zuckert, Plato's Philosophers: The Coherence of the Dialogues, University of Chicago Press (Chicago: 2009), pp. 243-244.