Note 87 — Chapter XXVIII · THEÆTETUS.

I borrow here a striking passage from Dugald Stewart, which illustrates both the passage in Plato’s text, and the general question as to the relativity of Cognition. Here, the fact of relative Cognition is brought out most conspicuously on its intellectual side, not on its perceptive side. The fact of sense is the same to all, and therefore, though really relative, has more the look of an absolute; but the mental associations with that fact are different with different persons, and therefore are more obviously and palpably relative. — Dugald Stewart, First Preliminary Dissertation to Encyclopæd. Britannica, pp. 66, 8th ed.

“To this reference of the sensation of colour to the external object, I can think of nothing so analogous as the feelings we experience in surveying a library of books. We speak of the volumes piled up on its shelves as treasures or magazines of the knowledge of past ages; and contemplate them with gratitude and reverence as inexhaustible sources of instruction and delight to the mind. Even in looking at a page of print or manuscript, we are apt to say that the ideas we acquire are received by the sense of sight; and we are scarcely conscious of a metaphor when we apply this language. On such occasions we seldom recollect that nothing is perceived by the eye but a multitude of black strokes drawn upon white paper, and that it is our own acquired habits which communicate to these strokes the whole of that significancy whereby they are distinguished from the unmeaning scrawling of an infant. The knowledge which we conceive to be preserved in books, like the fragrance of a rose, or the gilding of the clouds, depends, for its existence, on the relation between the object and the percipient mind: and the only difference between the two cases is, that, in the one, this relation is the local and temporary effect of conventional habits: in the other, it is the universal and the unchangeable work of nature.… What has now been remarked with respect to written characters, may be extended very nearly to oral language. When we listen to the discourse of a public speaker, eloquence and persuasion seem to issue from his lips; and we are little aware that we ourselves infuse the soul into every word that he utters. The case is exactly the same when we enjoy the conversation of a friend. We ascribe the charm entirely to his voice and accents; but without our co-operation, its potency would vanish. How very small the comparative proportion is, which in such cases the words spoken contribute to the intellectual and moral effect, I have elsewhere endeavoured to show.”