The confession of Sokrates that neither he nor any other person in his experience knows what virtue is--that it must be made a subject of special and deliberate investigation--and that no man can know what justice, or any other part of virtue is, unless he first knows what virtue as a whole is[32]--are matters to be kept in mind also, as contrasting with other portions of the Platonic dialogues, wherein virtue, justice, &c., are tacitly assumed (according to the received habit) as matters known and understood. The contributions which we obtain from the Menon towards finding out the Platonic notion of virtue, are negative rather than positive. The comments of Sokrates upon Menon's first definition include the doctrine often announced in Plato--That no man by nature desires suffering or evil; every man desires good: if he seeks or pursues suffering or evil, he does so merely from error or ignorance, mistaking it for good.[33] This is true, undoubtedly, if we mean what is good or evil for himself: and if by good or evil we mean (according to the doctrine enforced by Sokrates in the Protagoras) the result of items of pleasure and pain, rightly estimated and compared by the Measuring Reason. Every man naturally desires pleasure, and the means of acquiring pleasure, for himself: every man naturally shrinks from pain, or the causes of pain, to himself: every one compares and measures the items of each with more or less wisdom and impartiality. But the proposition is not true, if we mean what is good or evil for others: and if by good we mean (as Sokrates is made to declare in the Gorgias) something apart from pleasure, and by evil something apart from pain (understanding pleasure and pain in their largest sense). A man sometimes desires what is good for others, sometimes what is evil for others, as the case may be. Plato's observation therefore cannot be admitted--That as to the wish or desire, all men are alike: one man is no better than another.[34] [Footnote 32: Plato, Menon, p. 79 B-C. [Greek: tê\n ga\r dikaiosu/nên mo/rion phê\| a)retê=s ei)=nai kai\ e(/kasta tou/tôn. . . . oi)/ei tina ei)de/nai mo/rion a)retê=s o(/ ti e)/stin, au)tê\n mê\ ei)do/ta? Ou)k e)/moige dokei=.]] [Footnote 33: Plato, Menon, p. 77.] [Footnote 34: Plato, Menon, p. 78 B. [Greek: to\ me\n bou/lesthai pa=sin u(pa/rchei, kai\ tau/tê| ge ou)de\n o( e(/teros tou= e(te/rou belti/ôn.]] [Side-note: Sokrates requires knowledge as the principal condition of virtue, but does not determine knowledge, of what?]