It would be too sanguine to expect the real nature of pleasure and pain to be exhaustively defined in any formula such as the above. From a theoretical point of view grave objections may undoubtedly be raised against Marshall’s theory as well as against every general interpretation of emotional states. It may even be admitted, and we desire to admit it as soon as possible, that in several cases it seems extremely difficult to derive the feeling-tone of even the simplest sensations from the proportion between “energy given out and energy received.”[52] But since, as far as we can see, similar difficulties meet us in the application of every existing emotional theory, for the present we must consider the constructions of Mr. Marshall, notwithstanding their speculative and necessarily unsafe character, as affording us the most consistent explanation of the hedonic phenomena. In an earlier work, _Förstudier till en konstfilosofi_ (A Preliminary Study for a Philosophy of Art), I have tried to discuss and refute some of the arguments which can be adduced against this theory. In the present work such a theoretic digression would lead us too far away from the main subject. For a right understanding of the relation between feeling and “expressional” movements it is not necessary, we believe, to adopt exclusively any one of the emotional theories. We shall be quite content if it is admitted that Mr. Marshall’s interpretation affords us a scheme or formula by the aid of which we can account, if not for the nature, at least for the external manifestations of our feelings. In applying his definitions to the various kinds of pleasure and pain, Mr. Marshall has recourse to three important principles, viz. the limited amount of energy which our system is capable of developing at any given moment, the storage of surplus supplies of nourishment, and the transference of energy from one organ to another. By referring to these principles he has been able to bring under his explanation those feelings which seem to correspond not to “activities,” but to “states.”[53] As is well known, Hamilton had already pointed out the important, though unsuspected, element of activity which is involved in our enjoyment of _dolce far niente_.[54] But with the physiology at his command he could scarcely have explained why rest after heavy work is always accompanied by eminently pleasurable feelings. If it be assumed, however, that in the case of psychical effort, _e.g._, the call upon our limited fund of energy has reduced the vegetative functions to inactivity, and that this inactivity has caused a storage of nutritive supply, then it is self-evident that the vegetative functions, as soon as the one-sided effort has ceased, must discharge their surplus in movements of a pleasurable character.