Waxen memorial tablet in the mind, on which past impressions are engraved. False opinion consists in wrongly identifying present sensations with past impressions.
Let us look again in another direction (continues Sokrates). We have been hasty in our concessions. Is it really impossible for a man to conceive, that a thing, which he knows, is another thing which he does not know? Let us see. Grant me the hypothesis (for the sake of illustration), that each man has in his mind a waxen tablet — the wax of one tablet being larger, firmer, cleaner, and better in every way, than that of another: the gift of Mnemosynê, for inscribing and registering our sensible perceptions and thoughts. Every man remembers and knows these, so long as the impressions of them remain upon his tablet: as soon as they are blotted out, he has forgotten them and no longer knows them.[109] Now false opinion may occur thus. A man having inscribed on his memorial tablet the impressions of two objects A and B, which he has seen before, may come to see one of these objects again; but he may by mistake identify the present sensation with the wrong past impression, or with that past impression to which it does not belong. Thus on seeing A, he may erroneously identify it with the past impression B, instead of A: or vice versâ.[110] False opinion will thus lie, not in the conjunction or identification of sensations with sensations — nor of thoughts (or past impressions) with thoughts — but in that of present sensations with past impressions or thoughts.[111]
[109] Plato, Theæt. p. 191 C. κήρινον ἐκμογεῖον.
[110] Plato, Theæt. p. 193-194.
[111] Plato, Theæt. p. 195 D.
Sokrates refutes this assumption. Dilemma. Either false opinion is impossible, or else a man may know what he does not know.
Having laid this down, however, Sokrates immediately proceeds to refute it. In point of fact, false conceptions are found to prevail, not only in the wrong identification of present sensations with past impressions or thoughts, but also in the wrong identification of one past impression or thought with another. Thus a man, who has clearly engraved on his memorial tablet the conceptions of five, seven, eleven, twelve, — may nevertheless, when asked what is the sum of seven and five, commit error and answer eleven: thus mistaking eleven for twelve.
We are thus placed in this dilemma — Either false opinion is an impossibility:— Or else, it is possible that what a man knows, he may not know. Which of the two do you choose?[112]
[112] Plato, Theæt. p. 196 C. νῦν δὲ ἤτοι οὐκ ἔστι ψευδὴς δόξα, ἢ ἅ τις οἶδεν, οἷόν τε μὴ εἰδέναι· καὶ τούτων πότερα αἱρεῖ;
He draws distinction between possessing knowledge, and having it actually in hand. Simile of the pigeon-cage with caught pigeons turned into it and flying about.