‘It is, however, certain, that sight, apposited with interest, can retain tolerably exact copies of sensations, especially if not too complex; such as of the human countenance and figure. Yet the voice will convince us, when the countenance will not; and he is reckoned an excellent painter, and no ordinary genius, who can make a tolerable likeness from memory. Nay, more, it is a conspicuous proof of the inaccuracy of visual ideas, that it is an effort of consummate art, attained by many years’ practice, to take a strict likeness of the human countenance, even when the object is present; and among those cases, where the wilful cheat of flattery has been avoided, we still find in how very few instances the best painters produce a likeness up to the life, though practice and interest join in the attempt. ‘I imagine an ordinary person would find it very difficult, supposing he had some knowledge of drawing, to afford, from memory, a tolerable sketch of such a familiar object as his curtain, his carpet, or his dressing-gown, if the pattern of either be at all various or irregular; yet he will instantly tell, with precision, either if his snuff or his wine has not the same character it had yesterday, though both these are compounds. ‘Beyond all this I may observe, that a draper, who is in the daily habit of such comparisons, cannot carry in his mind the particular shade of a colour during a second of time; and has no certainty of tolerably matching two simple colours, except by placing the patterns in contact.’—_Essay on Consciousness_, p. 303