Pleasure and Pain show characteristics which are not noticeable in the generally recognized sensations.
11. Each of the typical sensations has a very special means of production by which it, and it only, is brought into consciousness. None of them have the characteristic which is observable in Pleasure-Pain, that they are aroused by the widest range of psychic occurrences.
Sensations are pleasurable and painful. Pains, indeed, as we see, are so closely related to sensations that an attempt is made to bring them together in classification.
But Emotions also are pre-eminently pleasure-pain colored. Pleasure is, in common parlance, spoken of as an emotion; and emotions are usually treated by English psychologists together with pleasure and pain.
Intellectual pleasures and intellectual pains, again, are well known to all thoughtful people.
Certainly we have here phenomena very different from anything noticeable with the recognized sensations. We never, for instance, have a cold thought as we have a painful thought or a sonorous emotion as we have a pleasurable emotion.
12. Under continuation of stimulative conditions, the typical sensations do not habitually change from one form to another. A definite stimulus does not habitually alter from a pressure into a sound, nor from a sound into a brightness. To be sure, water which feels hot when the hand is first plunged in, may soon seem none too warm, but it does not become cold unless there is a real change of the conditions of stimulation.
But under continuation of stimulative conditions, pleasure habitually fades into pain, although there are some relatively few exceptions, probably traceable, as I have elsewhere argued, to alterations in the system which really bring about a change in what appear to be continuous stimulative conditions.
13. Again, in the case of ordinary sensations, within the limits of normal activity, increasing or diminishing intensity of physical stimulation brings corresponding alterations of psychic activity, although the relation is complex and not simple. But with Pleasure-Pain the case is quite different. An increase of
