our other senses. Having so gained such light and data as we may, inasmuch as all copies ought to be traceable to originals of some kind and of some former period however remote (and in instincts they are very remote), we shall then examine how we may account for the far more difficult order of central and aesthetic pains and pleasures.
We are now to hunt for every phenomenon of pleasure or pain due directly to excitation of afferent nerves simultaneously with the stimulation of our other sensations — sight, sound, and so on. Every manner of agreeableness or disagreeableness not strictly of this order we are to throw out into a category of their own, to be explained afterward, yet in a manner entirely in accord with the doctrine of specific pleasure and pain activities. We are well aware of the meagreness of proportion which the aesthetic sensations which we shall discover will bear to the immense bulk of our associative or central aesthetics which we must throw out, but so also does our intellectual life as a whole outmeasure in like proportion the original experiences from which it has sprung.
We will begin with color. We know that light of any color, if sufficiently intense, will cause pain. Our hypothesis of specific pain nerves explains this. But we do not know that light of any single color, and of intensity less than will cause positive bodily pain from abnormal disturbances, will be accompanied normally and invariably either with agreeableness or disagreeableness. Undoubtedly our 'like' or 'dislike' often does accompany certain colors, which otherwise apparently are the sole objects of presentation. But these 'likes' may be indirect results of retinal stimulation. The 'explosion' of the cortex cells which, fired by the retinal currents, give us the color, may overflow to other regions and cells, which, consequently but secondarily, give us the 'like' or 'dislike.' That is, these aesthetics may be associated phenomena such as we are at present to neglect. Let me illustrate. The other day our laboratory received a large pile of "Bradley's Color-Sheets." They present each three or four square feet of uniform tint, and the pile contains a sample of nearly every possible tint and shade.
