§ 3. Conative and Iledonic Aspect of the Sensation-Reflex.— The movements arising from senseimpulses display in a simple and distinct manner an antithesis which pervades all manifestations of mind. They are directed either, on the one hand, to the removal, avoidance, or abatement of the stimulation which excites them, or, on the other, to its detention, maintenance, or increase. The first kind of reaction may be called positive, and the second negative. The psychical states which find expression in these antithetic types of movement, show a corresponding contrast of a twofold character. The reaction of avoidance or repulsion is the outward manifestation of disagreeable consciousness, and also of aversion, or, as Hobbes would say, of "endeavour fromward;" the positive reaction is the manifestation of agreeable consciousness and also of appetition, or "endeavour toward." Appetition and aversion are the fundamentally antithetic directions of psychical activity; their contrast is a contrast which belongs to the conative or striving aspect of consciousness. Pleasure and displeasure are the fundamental antithetic modes of feeling-tone. Their contrast is a contrast which belongs to the hedonic aspect of consciousness. In the purely sensory impulse, appetition always actually coincides with pleasure and aversion always actually coincides with pain. At higher levels of psychical life, the coincidence between positive conation and positive tone of feeling, and between negative conation and negative tone of feeling is by no means complete. After a fashion, the sensation-reflex may be described as an activity inasmuch as it has a conative aspect in the way of appetition or aversion. But the activity involved is of a rudimentary and primitive kind, just as the process itself is of a rudimentary and primitive kind. The sensation-reflex consists in a single simultaneous act; in this respect it is contrasted with perceptual process, which may, and usually does, combine a series of distinct and successive acts in the unity of a single action directed towards a single end. Thus, in the case of perceptual activity, we may speak of progress towards an end, which may or may not be interrupted or obstructed in its course. In the case of the sensation-reflex, on the contrary, the word "progress" has little or no meaning. It is for this reason that in it appetitive conation and agreeable feeling completely coincide. This is not the case in perceptual process, because disagreeable feeling may arise through obstruction of appetitive activity, which none the less remains appetitive although it has become disagreeably toned. We are endeavouring to hit the nail on the head even when we miss it.

We may briefly describe the physiological process involved in a sensation-reflex as follows. A stimulus disturbs the equilibrium of the nervous system. The subsequent process consists in the recovery of nervous equilibrium. When this is accomplished the end of the whole activity is attained, and it ceases. To put it simply, the excitement is allayed. The tendency to equilibrium is the physiological correlate of what on the psychical side we call conation,—the striving aspect of consciousness. But the nervous system may regain its balance in two opposite ways. It may be that it can only do so by removal of the stimulation which starts the whole process. On the other hand, it may happen that the continuance of the stimulation for a longer or shorter time is a positive condition of the reattainment of equilibrium. In the first case, we have pain and aversion; in the second, pleasure and appetition. As a rule, the more important is the perceptual function of a sensation, the less emphatic is its feeling-tone, and the more it approximates to a mere sensation concerned in merely sensory reaction, the more emphatic is its feeling-tone.

§ 4. Relative Purity of Sensation-Reflex.—The same sensation may, by its mere existence as a momentary experience, issue or tend to issue in a certain movement, and at the same time it may also determine action by its significance. Thus the perceptual may mingle with the sensational impulse, so that in practice it may sometimes be difficult to draw the line between them. The two modes of consciousness blend in intricate ways and in varying degrees.* In general, they bear an inverse ratio to each other. The lower we descend in the scale of animal life, the more important is sensation; the higher we ascend, the more important is perception. It should, however, be clearly understood that in theory the distinction between them is sharp and clear. This is peculiarly evident when the perceptual impulse depending on the meaning of a sensation is contrary to the sensational impulse itself, as when we repress a coming sneeze.

* This applies almost, if not quite, universally to the developed human consciousness. The nearest approach to the pure sensation-reflex in adult human beings is the reaction which accompanies intense bodily pain, especially if it occurs suddenly without the subject being prepared for it beforehand,