But again, with hearing and sight, or in the further bases of motion moving itself and heat burning itself, and all other actions of the sort, the fact must appear incredible to some, but perhaps not to others. So what we want, my friend, is some great man who will determine to our satisfaction in every respect whether there is nothing in nature so constituted as to have its own faculty applicable to itself, and not only some other object, or whether there are some such, and others not such; and whether, again, if there are things that have such relation to themselves, they include a science which we assert to be temperance. For my part, I distrust my own competence to determine these questions, and hence I am neither able to affirm whether it is possible that there should be a science of science, nor willing, let it be ever so true, to acknowledge this to be temperance until I have made out whether such a thing as this would benefit us or not. For, you see, I have a presentiment that temperance is something beneficial and good; and you, therefore, son of Callaeschrus—since you lay it down that temperance is this very science of science, and moreover of the lack of science—shall first indicate the possibility, as I put it just now, and then the benefit added to the possibility, of such a thing; and perhaps you will then satisfy me that your definition of temperance is correct. Now when Critias heard this and saw me in a difficulty, he seemed to me—just as the sight of someone yawning opposite causes people to be affected in the same way—to be compelled by the sense of my difficulty to be caught in a difficulty himself. And so, since he usually contrived to distinguish himself, he was too ashamed to bring himself to admit to me before the company that he was unable to determine the questions with which I challenged him, and he made a very indistinct reply in order to conceal his difficulty. Then I, to forward the discussion, remarked: Well, if you prefer, Critias, let us concede for the moment that there may possibly be a science of science : some other time we shall consider whether such is the fact or not. Come then; suppose it is perfectly possible: how is one helped thereby to know what one knows and does not know? For this, you are aware, we said Footnote 1Plat. Charm. 167a. was the meaning of self-knowledge and temperance, did we not? Certainly, he said; and it must surely follow, Socrates; for if a man has a science which knows itself, he will be similar himself to that which he has. For instance, he who has swiftness will be swift, he who has beauty will be beautiful, and he who has knowledge will know; and when he has knowledge that is of itself, he will then, surely, be in the position of knowing himself. I do not dispute, I said, that when a man has that which knows itself he will know himself; but having that, how is he bound to know what he knows and what he does not know?