Still an element of knowledge is wanting which Critias is readily induced to admit at the suggestion of Socrates; and, in the spirit of Socrates and of Greek life generally, proposes as a fifth definition, (5) Temperance is self-knowledge. But all sciences have a subject: number is the subject of arithmetic, health of medicine—what is the subject of temperance or wisdom? The answer is that (6) Temperance is the knowledge of what a man knows and of what he does not know.
