[10] Plato, Charm. 163 C-D. τὰ καλῶς καὶ ὠφελίμως ποιούμενα … οἰκεῖα μόνα τὰ τοιαῦτα ἡγεῖσθαι, τὰ δὲ βλαβερὰ πάντα ἀλλότρια … ὅτι τὰ οἰκεῖά τε καὶ τὰ αὑτοῦ ἀγαθὰ καλοίης, καὶ τὰς τῶν ἀγαθῶν ποιήσεις πράξεις.
[11] Plato, Charm. 163 E. τὴν τῶν ἀγαθῶν πρᾶξιν σωφροσύνην εἶναι σαφῶς σοι διορίζομαι.
Fourth answer, by Kritias. Temperance consists in self-knowledge.
Sokr. — Perhaps it is. But does the well-doer always and certainly know that he is doing well? Does the temperate man know his own temperance? Krit. — He certainly must. Indeed I think that the essence of temperance is, Self-knowledge. Know thyself is the precept of the Delphian God, who means thereby the same as if he had said — Be temperate. I now put aside all that I have said before, and take up this new position, That temperance consists in a man’s knowing himself. If you do not admit it, I challenge your cross-examination.[12]
[12] Plato, Charm. 164-165.
Questions of Sokrates thereupon. What good does self-knowledge procure for us? What is the object known, in this case? Answer: There is no object of knowledge, distinct from the knowledge itself.
Sokr. — I cannot tell you whether I admit it or not, until I have investigated. You address me as if I professed to know the subject: but it is because I do not know, that I examine, in conjunction with you, each successive answer.[13] If temperance consists in knowing, it must be a knowledge of something. Krit. — It is so: it is knowledge of a man’s self. Sokr. — What good does this knowledge procure for us? as medical knowledge procures for us health — architectural knowledge, buildings, &c.? Krit. — It has no object positive result of analogous character: but neither have arithmetic nor geometry. Sokr. — True, but in arithmetic and geometry, we can at least indicate a something known, distinct from the knowledge. Number and proportion are distinct from arithmetic, the science which takes cognizance of them. Now what is that, of which temperance is the knowledge, — distinct from temperance itself? Krit. — It is on this very point that temperance differs from all the other cognitions. Each of the others is knowledge of something different from itself, but not knowledge of itself: while temperance is knowledge of all the other sciences and of itself also.[14] Sokr. — If this be so, it will of course be a knowledge of ignorance, as well as a knowledge of knowledge? Krit. — Certainly.
[13] Plato, Charm. 165 C.
[14] Plato, Charm. 166 C. αἱ μὲν ἄλλαι πᾶσαι ἄλλου εἰσὶν ἐπιστῆμαι, ἑαυτῶν δ’ οὔ· ἡ δὲ μόνη τῶν τε ἄλλων ἐπιστημῶν ἐπιστήμη ἐστὶ καὶ αὐτὴ ἑαυτης. So also 166 E.
Sokrates doubts the possibility of any knowledge, without a given cognitum as its object. Analogies to prove that knowledge of knowledge is impossible.