§ 6. General Theory.—Whatever conditions further and favour conation in the attainment of its end, yield pleasure. Whatever conditions obstruct conation in the attainment of its end, are sources of displeasure. This is the widest generalisation which we can frame, from a purely psychological point of view, as regards the conditions of pleasure and displeasure respectively. Its application to the feeling-tone of sensation is already contained in the last section. A pleasing sense-experience operates as a positive factor satisfying the cognitive tendency or quasicognitive tendency which is essentially connected with it. On the contrary, an unpleasing sense-experience operates as a positive factor thwarting the cognitive tendency or quasicognitive tendency essentially connected with it. This is at the best only a vague explanation of sense pleasure-pain. It can only be regarded as being an explanation at all on one assumption. If it is supposed that, first, pleasure exists, and that, subsequently to its occurrence, the cognitive tendency arises as a consequence, it is a logical circle to explain the pleasure by reference to the conation. But, as a matter of fact, there seems to be no reason whatever for supposing that feeling-tone and conation are separated in time. From the very beginning they appear to coincide. From the very beginning a pleasing process is a process which tends to maintain itself.

We may hope to attain a more definite insight into the ultimate conditions which determine the feeling-tone of sensation from the physiological side. But from that side we have not at present any direct knowledge of the nervous processes involved. We can only frame hypotheses to cover the psychological data.

If we attempt to translate into physiological language the general relations of pleasure and displeasure respectively to cognitive tendencies, perhaps the best result we can obtain is the following. Conation in general appears to correspond to a disturbance of nervous equilibrium, and its completed satisfaction to a restoration of equilibrium. The conditions of displeasure not only disturb nervous equilibrium, but also, so long as they continue, obstruct the processes by which it tends to be restored. On the other hand, the continuance of the conditions of pleasure is a factor positively operative in the restoration of equilibrium. It is evident that even if this view of the case be granted, there is still abundant room for further speculation as to the precise nature of the physiological processes corresponding to pleasure and displeasure respectively. The most favoured theories of the kind connect these opposite feeling-tones with the relations of wear and repair in the nervous system. Explanations based on this general principle assume many different forms; our ignorance of the exact nature of the complex chemical processes involved in assimilation and dissimilation of tissue, and of their connexion with functional activity and repose, leaves much room for speculation. The simplest form of statement is that when wear outruns repair the experience is displeasing, and that when repair outruns wear the experience is pleasing. On this view it is difficult to account for the fact that pleasures may be exhausting, and that when they are longcontinued, they diminish, and pass into displeasure. Mr. H. R. Marshall has propounded a theory which lays great stress on the building up of tissue during periods of functional repose. Pleasure, according to him, depends upon the building up of a surplus of stored energy acquired during the inaction of the organ. "Where this surplus does not exist or has been consumed, the corresponding experience will be virtually neutral, so long as repair keeps pace with wear in the course of functional activity. If wear outruns repair, the corresponding experience is unpleasant. There is much to be said in favour of this view, and Mr. Marshall has said it with great clearness and force. Fatigue is in general a source of disagreeable, and freshness of agreeable, experience. Of course, the fatigue or the freshness must be that of the special tissues engaged in the functional activity. ''After the quiet of the nighthours the birdsong, as we awake, is more than usually pleasurable; the rested eye sees beauty in all colours. The rubbing, at our morning bath, of the skin, which has not during the night felt the normal friction of our clothing; the flavour of some special food to which we have been accustomed, but which has not lately been tasted,—all are pleasurable." when too long continued, will become unpleasant, because the stored surplus is used up. What is a surplus relatively to one intensity of stimulation, will not be a surplus relatively to a higher intensity; hence by gradually increasing the intensity of a stimulus, we pass from pleasant to unpleasant phases of an experience. But along with these advantages the theory presents grave difficulties, if we attempt to base on it the whole explanation of the feeling-tone of sensation; and in my opinion it presents insuperable difficulties if we attempt to cover by its means all the pleasures and pains of perceptual and ideational activity. At present we are only concerned with sensation.

* A pleasant sensation, * Fain, Pleasure, and Aesthetics, p. 200.