"When we talk about iron or silver" (says Sokrates in the Platonic Phædrus, p. 263 A-B) "we are all of one mind, but when we talk about the Just and the Good we are all at variance with each other, and each man is at variance with himself". Compare an analogous passage, Alkibiad. I. p. 109. Here Plato himself recognises the verifications of sense as the main guarantee for accuracy: and the compared facts of sense, when select and simplified, as ensuring the nearest approach to unanimity among believers.] [Side-note: Arguments of Sokrates in examining this question. Divergence between one man and another arises, not merely from different sensual impressibility, but from mental and associative difference.] A loose adumbration of this doctrine is here given by Plato as the doctrine of Protagoras, in the words--Knowledge is sensible perception. To sift this doctrine is announced as his main purpose;[85] and we shall see how he performs the task. _Sokr._--Shall we admit, that when we perceive things by sight or hearing, we at the same time _know_ them all? When foreigners talk to us in a strange language, are we to say that we do not hear what they say, or that we both hear and know it? When unlettered men look at an inscription, shall we contend that they do not see the writing, or that they both see and know it? _Theætêt._--We shall say, under these supposed circumstances, that what we see and hear, we also know. We hear and we know the pitch and intonation of the foreigner's voice. The unlettered man sees, and also knows, the colour, size, forms, of the letters. But that which the schoolmaster and the interpreter could tell us respecting their meaning, _that_ we neither see, nor hear, nor know. _Sokr._--Excellent, Theætêtus. I have nothing to say against your answer.[86] [Footnote 85: Plato, Theætêt. p. 163 A. [Greek: ei)s ga\r tou=to/ pou pa=s o( lo/gos ê(mi=n e)/teine, kai\ tou/tou cha/rin ta\ polla\ kai\ a)/topa tau=ta e)kinê/samen.]] [Footnote 86: Plato, Theætêt. p. 163 C.] This is an important question and answer, which Plato unfortunately does not follow up. It brings to view, though without fully unfolding, the distinction between what is really perceived by sense, and what is inferred from such perception: either through resemblance or through conjunctions of past experience treasured up in memory--or both together. Without having regard to such distinction, no one can discuss satisfactorily the question under debate.[87] Plato here abandons, moreover, the subjective variety of impression which he had before noticed as the characteristic of sense:--(the wind which blows cold, and the wine which tastes sweet, to one man, but not to another). Here it is assumed that all men hear the sounds, and see the written letters alike: the divergence between one man and another arises from the different prior condition of percipient minds, differing from each other in associative and reminiscent power.