Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/64

52 PSYCHOLOGY alternation of sensory and motor phases which is common to all psychical life, a certain sensation, comparatively in- tense, and a certain movement, definite enough to control that sensation, engage attention in immediate succession, to the more or less complete exclusion from attention of the other less intense sensations and more diffused movements that accompany them. Apart from this intervention of controlling movements, the presentation-continuum, how- ever much differentiated, would be for all purposes of know- ledge little better than the disconnected manifold for which Kant took it. At the same time it is to be remembered that the subject obtains command of particular movements out of all the mass involved in emotional expression only because such movements prove on occurrence adapted to control certain sensations. Before experience, and apart from heredity, there seems not only no scientific warrant for assuming any sort of practical prescience but also none for the hypothesis of a priori forms of knowledge. Of a pre-established harmony between the active and passive phases of consciousness we need none, or it may be safer to say at least indefinitely little. A sentient creature moves first of all because it feels, not because it intends. A long process, in which natural selection probably played the chief part at the outset subjective selection becoming more prominent as the process advanced must have been necessary to secure as much purposive movement as even a lobster displays. It seems impossible to except from this process the movements of the special sense-organs which are essential to our perception of external things. Here too subjective interest will explain, so far as psycho- logical explanation is possible, those syntheses of motor and sensory presentations which we call spatial perceptions and intuitions of material things. For example, some of the earliest lessons of this kind seem to be acquired, as we may presently see, in the process of exploring the body by means of the limbs, a process for which grounds in sub- jective interest can obviously never be wanting. The mere process of " association " whereby we may suppose the synthesis of presentations to be effected so that presentations originally in no way connected tend to move in consciousness together will confront us with its own problems later on. We need for the present only to bear in mind that the conjunction or continuity upon which the association primarily depends is one determined by the movements of attention, which movements in turn depend very largely upon the pleasure or pain that pre- sentations occasion. To some extent, however, there is no doubt that attention may pass non-voluntarily from one indifferent presentation to another, each being sufficiently intense to give what has been called a "shock of surprise," but not so intense as to awaken feeling to move for their de- tention or dismissal. But throughout the process of mental development, where we are concerned with what is new, the range of such indifference is probably small : indifferent presentations there will be, but that does not matter while there are others that are interesting to take the lead. Meaning Perception as a psychological term has received various, of per- though related, meanings for different writers. It is ception. gome ti mes used for the recognition of a sensation or move- ment as distinct from its mere presentation, and thus is said to imply the more or less definite revival of certain residua or re-presentations of past experience which re- sembled the present. More frequently it is used as the equivalent of what has been otherwise called the " localiza- tion and projection " of sensations, that is to say, a sensa- tion presented either as an affection of some part of our own body regarded as extended or as a state of some foreign body beyond it. According to the former usage, strictly taken, there might be perception without any spatial pre- sentation at all : a sensation that had been attended to a few times might be perceived as familiar. Such percept being a " presentative- representative " complex, and wholly sensory, we might symbolize it, details apart, as S + s, using S for the present sensation, and s for a former S re- presented. According to the latter usage, an entirely new sensation, provided it were complicated with motor experi- ences in the way required for its localization or projection, would become a perception. Such a perception might be roughly symbolized as X + (M+ m), or as X + m simply, M standing for actual movements, as in ocular adjustment, which in some cases might be only former movements re- presented or m. But as a matter of fact actual perception probably invariably includes both cases : impressions which we recognize we also localize or project, and impressions which are localized or projected are never entirely new, they are, at least, perceived as sounds or colours or aches, &c. It will, however, frequently happen that we are speci- ally concerned with only one side of the whole process, as is the case with a tea- taster or a colour-mixer on the one hand, or, on the other, with the patient who is perplexed to decide whether what he sees and hears is " subjective," or whether it is " real." Usually we have more trouble to discriminate the quality of an impression than to fix it spatially ; indeed this latter process was taken for granted by most psychologists till recently. But, however little the two sides are actually separated, it is important to mark their logical distinctness, and it would be well if we had a precise name for each. In any other science save psychology such names would be at once forthcoming ; but it seems the fate of this science to be restricted in its terminology to the ill -defined and well-worn currency of common speech, with which every psychologist feels at liberty to do what is right in his own eyes, at least within the wide range which a loose connotation allows. If there were any hope of their general acceptance we might pro- pose to call the first-mentioned process the assimilation or recognition of an impression, and might apply the term localization to its spatial fixation, without distinguishing between the body and space beyond, a matter of the less importance as projection hardly enters into primitive spatial experience. But there is still a distinction called for : perception as we now know it involves not only localization, or "spatial reference," as it is not very happily termed, but " objective reference " as well. We may perceive sound or light without any presentation of that which sounds or shines ; but none the less we do not regard such sound or light as merely the object of our attention, as having only immanent existence, but as the quality or change or state of a thing, an object distinct not only from the subject attending but from all presentations whatever to which it attends. Here again the actual separation is impossible, because this factor in perception has been so intertwined throughout our mental develop- ment with the other two. Still a careful psychological ana- lysis will show that such " reification," as we might almost call it, has depended on special circumstances, which we can at any rate conceive absent. These special circumstances are briefly the constant conjunctions and successions of impressions, for which psychology can give no reason, and the constant movements to which they prompt. Thus we receive together, e.g., those impressions we now recognize as severally the scent, colour, and " feel " of the rose we pluck and handle. We might call each a " percept," and the whole a "complex percept." But there is more in such a complex than a sum of partial percepts ; there is the apprehension or intuition of the rose as a thing having this scent, colour, and texture. We have, then, under perception to consider (i.) the assimilation and (ii.) the localization of impressions, and (iii.) the intuition of things. The range of the terms assimilation or recognition of