[25] Though the advice here given by Plato about the principles of classification is very judicious, yet he has himself in this same dialogue set an example of repugnance to act upon it (Sophist. p. 231 A-B.) In following out his own descending series of partitions, he finds that the Sophist corresponds with the great mental purifier — the person who applies the Elenchus or cross-examining test, to youthful minds, so as to clear out that false persuasion of knowledge which is the great bar to all improvement. But though brought by his own process to this point, Plato shrinks from admitting it. His dislike towards the Sophist will not allow him. “The Sophist is indeed” (he says) “very like to this grand educator: but so also a wolf is very like to a dog — the most savage of animals to the most gentle. We must always be extremely careful about these likenesses: the whole body of them are most slippery. Still we cannot help admitting the Sophist to represent this improving process — that is, the high and true bred Sophist.”
It will be seen that Plato’s remark here about ὁμοιότητες contradicts what he had himself said before (p. 227 B). The reluctance to rank dog and wolf together, in the same class, is an exact specimen of that very mistake which he had been just pointing out for correction. The scientific resemblance between the two animals is very close; but the antithesis of sentiment, felt by men towards the one and the other, is extreme.
The purifier — a species under the genus discriminator — separates good from evil. Evil is of two sorts; the worst sort is, Ignorance, mistaking itself for knowledge.
After these just remarks on classification generally, the Eleate pursues the subdivision of his own theme. To purify the mind is to get rid of the evil, and retain or improve the good. Now evil is of two sorts — disease (injustice, intemperance, cowardice, &c.) and ignorance. Disease, which in the body is dealt with by the physician, is in the mind dealt with by the judicial tribunal: ignorance (corresponding to ugliness, awkwardness, disability, in the body, which it is the business of the gymnastic trainer to correct) falls under the treatment of the teacher or instructor.[26] Ignorance again may be distributed into two heads: one, though special, being so grave as to counterbalance all the rest, and requiring to be set apart by itself — that is — ignorance accompanied with the false persuasion of knowledge.[27]
[26] Plato, Sophist. pp. 228-229.
[27] Plat. Soph. p. 229 C. Ἀγνοίας δ’ οὖν μέγα τί μοι δοκῶ καὶ χαλεπὸν ἀφωρισμένον ὁρᾷν εἶδος, πᾶσι τοῖς ἄλλοις αὐτῆς ἀντίσταθμον μέρεσι … Τὸ μὴ κατειδότα τι, δοκεῖν εἰδέναι.
Exhortation is useless against this worst mode of evil. Cross-examination, the shock of the Elenchus, must be brought to bear upon it. This is the sovereign purifier.
To meet this special and gravest case of ignorance, we must recognise a special division of the art of instruction or education. Exhortation, which is the common mode of instruction, and which was employed by our forefathers universally, is of no avail against this false persuasion of knowledge: which can only be approached and cured by the Elenchus, or philosophical cross-examination. So long as a man believes himself to be wise, you may lecture for ever without making impression upon him: you do no good by supplying food when the stomach is sick. But the examiner, questioning him upon those subjects which he professes to know, soon entangles him in contradictions with himself, making him feel with shame and humiliation his own real ignorance. After having been thus disabused — a painful but indispensable process, not to be accomplished except by the Elenchus — his mind becomes open and teachable, so that positive instruction may be communicated to him with profit. The Elenchus is the grand and sovereign purification: whoever has not been subjected to it, were he even the Great King, is impure, unschooled, and incompetent for genuine happiness.[28]
[28] Plato, Sophist. p. 230 D-E.
The application of this Elenchus is the work of the Sophist, looked at on its best side. But looked at as he really is, he is a juggler who teaches pupils to dispute about every thing — who palms off falsehood for truth.