[40] Plato, Republ. iv. 433, vi. 496 C, viii. 550 A; Gorgias, 526 C. Compare also Timæus, 72 A, Xen, Mem. ii. 9, 1.
Self-knowledge is here declared to be impossible.
Again, another definition given by Kritias is, That temperance consists in knowing yourself, or in self-knowledge. In commenting upon this definition, Sokrates makes out — first, that self-knowledge is impossible: next, that if possible, it would be useless. You cannot know yourself, he argues: you cannot know what you know, and what you do not know: to say that you know what you know, is either tautological or untrue — to say that you know what you do not know, is a contradiction. All cognition must be cognition of something distinct from yourself: it is a relative term which must have some correlate, and cannot be its own correlate: you cannot have cognition of cognition, still less cognition of non-cognition.
In other dialogues, Sokrates declares self-knowledge to be essential and inestimable. Necessity for the student to have presented to him dissentient points of view.
This is an important point of view, which I shall discuss more at length when I come to the Platonic Theætetus. I bring it to view here only as contrasting with different language held by the Platonic Sokrates in other dialogues; where he insists on the great value and indispensable necessity of self-knowledge, as a preliminary to all other knowledge — upon the duty of eradicating from men’s minds that false persuasion of their own knowledge which they universally cherished — and upon the importance of forcing them to know their own ignorance as well as their own knowledge. In the face of this last purpose, so frequently avowed by the Platonic Sokrates (indirectly even in this very dialogue),[41] we remark a material discrepancy, when he here proclaims self-knowledge to be impossible. We must judge every dialogue by itself, illustrating it when practicable by comparison with others, but not assuming consistence between them as a postulate à priori. It is a part of Plato’s dramatic and tentative mode of philosophising to work out different ethical points of view, and to have present to his mind one or other of them, with peculiar force in each different dialogue. The subject is thus brought before us on all its sides, and the reader is familiarised with what a dialectician might say, whether capable of being refuted or not. Inconsistency between one dialogue and another is not a fault in the Platonic dialogues of Search; but is, on the contrary, a part of the training process, for any student who is destined to acquire that full mastery of question and answer which Plato regards as the characteristic test of knowledge. It is a puzzle and provocative to the internal meditation of the student.
[41] Plato, Charm. 166 D.
Courage and Temperance are shown to have no distinct meaning, except as founded on the general cognizance of good and evil.
In analyzing the Lachês, we observed that the definition of courage given by Nikias was shown by Sokrates to have no meaning, except in so far as it coincided with the general knowledge or cognition of good and evil. Here, too, in the Charmidês, we are brought in the last result to the same terminus — the general cognition of good and evil. But Temperance, as previously good and defined, is not comprehended under that cognition, and is therefore pronounced to be unprofitable.
Distinction made between the special sciences and the science of Good and Evil. Without this last, the special sciences are of no use.
This cognition of good and evil — the science of the profitable — is here (in the Charmidês) proclaimed by Sokrates to have a place of its own among the other sciences; and even to be first among them, essentially necessary to supervise and direct them, as it had been declared in Alkibiadês II. Now the same supervising place and directorship had been claimed by Kritias for Temperance as he defines it — that is, self-knowledge, or the cognition of our cognitions and non-cognitions. But Sokrates doubts even the reality of such self-knowledge: and granting for argument’s sake that it exists, he still does not see how it can be profitable. For the utmost which its supervision can ensure would be, that each description of work shall be scientifically done, by the skilful man, and not by the unskilful. But it is not true, absolutely speaking (he argues), that acting scientifically or with knowledge is sufficient for well doing or for happiness: for the question must next be asked — Knowledge — of what? Not knowledge of leather-cutting, carpenter’s or brazier’s work, arithmetic, or even medicine: these, and many others, a man may possess, and may act according to them; but still he will not attain the end of being happy. All cognitions contribute in greater or less proportion towards that end: but what contributes most, and most essentially, is the cognition of good and evil, without which all the rest are insufficient. Of this last-mentioned cognition or science, it is the special object to ensure profit or benefit:[42] to take care that everything done by the other sciences shall be done well or in a manner conducing towards the end Happiness. After this, there is no province left for temperance — i.e., self-knowledge, or the knowledge of cognitions and non-cognitions: no assignable way in which it can yield any benefit.[43]