[Footnote 180: Plato, Republic, vii. pp. 538 D-539. [Greek: o(/tan to\n ou(/tôs e)/chonta e)ltho\n e)rô/têma e)/rêtai, ti/ e)sti to\ kalo/n, kai\ a)pokrina/menon o(\ tou= nomothetou= ê)/kouen e)xelegchê=| o( lo/gos, kai\ polla/kis kai\ pollachê= e)le/gchôn ei)s do/xan katabalê=| ô(s tou=to ou)de\n ma/llon kalo\n ê)\ ai)schro\n, kai\ peri\ dikai/ou ô(sau/tôs kai\ a)di/kou, kai\ a(\ ma/lista ê)=gen e)n timê=|], &c.] [Footnote 181: Plato, Repub. vii. p. 539 B.] Accordingly, we must not admit (says Plato) either young men, or men of ordinary untrained minds, to dialectic debate. We must admit none but mature persons, of sedate disposition, properly prepared: who will employ it not for mere disputation, but for the investigation of truth.[182] [Footnote 182: Plato, Repub. vii. p. 539 D.] [Side-note: Contradiction with the spirit of other dialogues--Parmenidês, &c.] Now the doctrine thus proclaimed, with the grounds upon which it rests--That dialectic debate is unsuitable and prejudicial to young men--distinctly contradict both the principles laid down by himself elsewhere, and the frequent indications of his own dialogues: not to mention the practice of Sokrates as described by Xenophon. In the Platonic Parmenidês, and Theætêtus, the season of youth is expressly pronounced to be that in which dialectic exercise is not merely appropriate, but indispensable to the subsequent attainment of truth.[183] Moreover, Plato puts into the mouth of Parmenides a specimen intentionally given to represent that dialectic exercise which will be profitable to youth. The specimen is one full of perplexing, though ingenious, subtleties: ending in establishing, by different trains of reasoning, the affirmative, as well as the negative, of several distinct conclusions. Not only it supplies no new positive certainty, but it appears to render any such consummation more distant and less attainable than ever.[184] It is therefore eminently open to the censure which Plato pronounces, in the passage just cited from his Republic, against dialectic as addressed to young men. The like remark may be made upon the numerous other dialogues (though less extreme in negative subtlety than the Parmenidês), wherein the Platonic Sokrates interrogates youths (or interrogates others, in the presence of youths) without any positive result: as in the Theætêtus, Charmidês, Lysis, Alkibiadês, Hippias, &c., to which we may add the conversations of the Xenophontic Sokrates with Euthydemus and others.[185] [Footnote 183: Plato, Parmenidês, pp. 135 D, 137 B. Theætêt. 146 A.