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not so intense as to awaken feeling to move for their detention 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.

Perception as a psychological term has various, though related, meanings with different writers. It sometimes means only the recognition of a sensation or movement as distinct from its original presentation. But more frequently it is used as the equivalent of what has been otherwise called the 'localisation and projection' of sensations-that is to say, of sensations apprehended either as affections of some part of our own body regarded as extended -a pin prick, for example-or as qualities of it or of some foreign body beyond it--for example, the colour of one's hand or of the pen in it. According to the former usage strictly taken, there might be perception without any spatial presentation at all; a sensation that had been attended to a few times being perceived as familiar. Such percept as a 'presentative-representative' complex and wholly sensory, we might symbolize, so far, as S+s, indicating by S the present sensation and by s the ground in past experience of its familiarity1. According to the latter usage, an entirely new sensation-if such were possible-provided it were complicated with motor experiences in the way required for its localisation or projection, would become a percept. Such a percept again 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 represented or m. But as a matter of fact actual perception probably invariably includes both meanings: impressions which we recognise we also localise or project, and impressions which are localised 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 specially 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 is 'subjective,' like the spectral dagger that bewildered Macbeth, or whether it is 'real.'

1 Cf. below, ch. vii, § 2.

But there is still a distinction called for: perception, as we now know it, involves not only recognition (or assimilation) and 'spatial reference,' as it is not very happily termed, but it usually involves 'reference' to a thing as well. We may perceive a sound or a light without any presentation of that which sounds or shines; but none the less we regard such sound or light as the quality or change or state of a something that is distinct not only from the subject attending but from all the impressions to which he is attending. Here again actual separation is impossible, because this 'objective reference' has been so intertwined throughout our mental development with the other two. Still a careful psychological analysis will shew 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, eg. those impressions we now recognise 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 (a) the recognition, and (b) the localisation, of impressions, and (c) the ‘intuition' of things.

Recognition of Impressions.

§ 2. The range of the terms recognition or assimilation of impressions is wide: between the simplest mental process they may be supposed to denote and the most complex there is a great difference. The penguin that watched unmoved the first landing of man upon its lonely rock becomes as wild and wary as more civilised fowl after two or three visits from its molester: it then recognises that featherless biped. His friends at home

1 Intuition is used here to denote a complex of simple percepts synthesized as a unity in space and time. But to speak instead of a complex or of an acquired percept does not adequately indicate either the unity or the 'ideal construction' that 'thinghood' implies. The German Anschauung is frequently used in a like

sense.

also recognise him though altered by years of peril and exposure. In the latter case some trick of voice or manner, some 'striking' feature, calls up and sustains a crowd of memories of the traveller in the past-events leading on to the present scene. The two recognitions are widely different, and it is from states of mind more like the latter than the former that psychologists have usually drawn their description of such simple perception. At the outset, they say, we have a primary presentation or impression P, and after sundry repetitions there remains a mass or a series of P residua, Pipap...; perception ensues when, sooner or later, Pn 'calls up' and associates itself with these representations or ideas. Much of our later perception awakens, no doubt, both distinct memories and distinct expectations. But, since these imply previous perceptions, it is obvious that the earliest form of recognition must be free from such associations, and so is not equivalent to the logical judgment, P, is a P. Assimilation involves retentiveness and differentiation, as we have seen, and prepares the way for re-presentation; but in itself there is no confronting the new with the old, no determination of likeness, and no subsequent classification'. The pure sensation we may regard as a psychological myth; and the simple image, or such sensation revived, seems equally mythical, as we may see later The nth sensation is not like the first: it is a change in a presentation-continuum that has itself been changed by those preceding; and it cannot with any propriety be said to reproduce these past sensations, for they never had the individuality which such reproduction implies. Nor does it associate with images like itself, since where there is association there must first have been distinctness, and what can be associated can also, for some good time at least, be dissociated.

on.

So far for expository convenience we have regarded recognition or simple perception as if it were an isolated process: in point of fact, like all other psychical processes, it is always an integral part of the larger whole, living experience. Hence in becoming familiar an impression acquires what has been well called 'primary meaning"; for it has only become familiar through attention and it has only been attended to because it interested the subject-affecting it pleasantly or painfully1 Cf. below, ch. vii, § 2.

2 Stout, Manual of Psychology, 3rd edn. (1913), pp. 182 f.

and so has acquired practical significance—merely cognitive significance has no place at this level1.

Localisation of Impressions: the factors involved.

3. To treat of the localisation of impressions is really to give an account of the steps by which the psychological individual comes to a knowledge of space. At the outset of such an inquiry it seems desirable first of all to make plain what lies within our purview, and what does not, lest we disturb the peace of those who, confounding philosophy and psychology, are ever eager to fight for or against the a priori character of this element of knowledge. That the knowledge of space is a priori in the epistemological sense it is no concern of the psychologist either to assert or to deny. Psychologically a priori, it certainly is not: not, that is to say, in the sense of being from the very beginning either implicitly or explicitly a factor in all presentation whatever. It will help to make this matter clearer if we distinguish what philosophers frequently confuse, viz. the concrete spatial experiences, constituting actual localisation for the individual, and the concept of space, at once abstract and ideal, based on what is found to be common in such experiences. A gannet's mind 'possessed of' a philosopher, if such a conceit may be allowed, would certainly afford its tenant very different spatial experiences from those he might share if he took up his quarters in a mole. So, any one who has revisited in after years a place from which he had been absent since childhood knows how largely a 'personal equation,' as it were, enters into his spatial perceptions. Or the same truth may be brought home to him if, walking with a friend more athletic than himself, they come upon a ditch, which both know to be twelve feet wide, but which the one feels he can clear by a jump and the other feels he cannot. In the concrete 'up' is much more than a different direction from 'along.' The hen-harrier, which cannot soar, is indifferent to a quarry a hundred feet above it, to which the peregrine, built for soaring, would at once give chase; but the hen-harrier is on the alert as soon as it descries prey that is on or near the ground.

In the concrete, the body is the origin or datum to which 1 Cf. ch. i, § 4, pp. 20 f.

all positions are referred, and thus 'here' for the individual percipient is an absolute position, one that has no counterpart in the thoroughgoing relativity of pure space. Also 'the bodysense' in contrast with what may be called 'the projecting senses' yields the further absolute distinction of internal and external, marking off the bodily self from its environment. The environing space, again, for the percipient, varies in character, intimacy, and even dimensions as perception recedes from the foreground towards the background, from objects to which we can adjust by changes of posture to objects only to be reached by locomotion. Moreover, our various bodily movements and their combinations constitute a network of co-ordinates, qualitatively distinguishable but geometrically, so to put it, both redundant and incomplete. It is a long way from these facts of perception, which the brutes share with us, to that scientific concept of space, as having three dimensions and no qualitative differences, which we have elaborated by the aid of thought and language; and which reason may see to be the logical presupposition of what in the order of mental development has chronologically preceded it. That the experience of space is not psychologically original seems obvious-quite apart from any successful explanation of its origin-from the mere consideration of its complexity. Thus we must have a plurality of objects-A out of B, B beside C, distant from D, between it and A, and so on; and all these relations of externality, juxtaposition, distance and internality imply further specialisation; for with a mere plurality of objects we have not straightway spatial relations. Juxtaposition, e.g. is, strictly speaking, only possible when the related objects form a sensible continuum; but, again, not any continuity is extensive. Now how has the perception of this complexity come about? We shall find that it depends on three factors, each of which is indispensable.

This

(a) The first condition of spatial experience seems to lie in what has been noted above as the extensity of sensation'. much we may allow is original; for the longer we reflect the more clearly we see that no combination or association of sensations varying only in intensity and quality, not even if motor presentations were among them, will account for this element in our spatial perception. A succession of touches a, b, 1 Cf. ch. iv, § 2, p. 78; ch. v, § 4, p. 116.

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