(E) Perception (cont.)
We may now consider the part which movement plays in elaborating the presentations of this dimensionless continuum into perceptions of space. In so doing we must bear in mind that this continuum implies the incopresentability of two impressions having the same local sign, but allows not only of the presentation of impressions of varying massiveness but of several distinct impressions at the same time. At regards the motor element itself, the first point of importance is the incopresentability and invariability of a series of auxilio-motor presentation, P1, P2, P3, P4. P1 cannot presented along with P2, and from P4, it is impossible to reach P1 again save through P3 and P2. Such a series, taken alone, could afford us, it is evident, nothing but the knowledge of an invariable sequence of impression which it was in our own power to produce. It psychological interest would lie solely in the fact that, whereas other impressions depend on an objective initiative, these depend on a subjective. But in the course of the movements necessary to the exploration of the bodyprobably our earliest lesson in special perceptionthese auxilio-motor presentations receive a new significance from the active and passive touches that accompany them, as they impart to these last significance they could never have alone.
It is only on the resulting complex that we have the presentations of position and of spatial magnitude. For space, though conceived as a coexistent continuum, excludes the notion of omnipresence or ubiquity ; two positions ld and lg must coexist, but they not strictly distinct positions so long as we conceive ourselves present in the same sense in both. But, if Fd and Fg are, e.g. two same sense in both. But, if Fd and Fg are, e.g., two impressions produced by compass-touching two different spots as l and lg on the hand or-arm, and we place a finger upon ld and move it to lg, experiencing thereby the series P1, P2, P3, P4, this series constitutes Ld and lg into positions and also invests Fd and Fg with a relation not or mere distinctness but of definite distance. The resulting complex perhaps admits of symbolization as follows:
PLACE DIAGRAM HERE
Here the first line represents a portion of the tactual continuum, Fd and Fg being distinct "feels,: if we may so say, or passive touches presented along with the fainter sensation of the exploring finger and P1 for the corresponding auxilio-motor object ; the rest of the succession, as not actually present at this stage but capable of revival from past explorations, is symbolized by the t t t and p2p3p4. When the series of movement is accompanied by active touches without passive there arises the distinction between ones own body and foreign bodies; when the initial movement of a series is accompanied by both active and passive touches, the final movement by active touches only, and the intermediate movements are unaccompanied by either, we get the further presentation of empty space lying between us and them, but only when by frequent experience of contracts along with these intermediate movements we have come to know all movement as not only succession but change of position. Thus active touches come at length to be projected, passive touches alone being localized in the stricter sense. But in actual fact, of course, the localization of one impression is not perfected before that of another is begun, and we must take care lest our necessarily meagre exposition give rise to the mistaken notion that localizing an impression consist wholly and solely in performing the particular movements necessary to add active touches to a group of passive impressions. That this cannot suffice is evident merely from the consideration that a single position out of relation to all other positions is a contradiction. Localization, though it depends on many special experiences of the kind described, is not like an artificial product which is completed a part at a time, but is essentially a growth, its several constituent localizations advancing together in definiteness and interconnexion. So far has this development advanced that we do not even imagine the special movements which the localization of an impression implies, that is to say, they are no longer distinctly represented as they would be if we definitely intended to make them : the past experiences are "retained," but too much blended in the mere perception to be appropriately spoken of as remembered or imaged.
Apropos of this almost instinctive character of even our earliest spatial perceptions it will be appropriate to animadvert on a misleading implication in the current use of such terms of such terms as "localization," "projection," "bodily reference," "spatial reference," and the like. The implication is that external space, or the body as extended, is in some sort presented or supposed apart from the localization, projection, or reference of impressions to such space. That it may be possible to put a book in its place on a shelf there must be (1) the book, and (2), distinct and apart from it, the place on the shelf. But in the evolution of our spatial experience impressions and positions are not thus presented apart. We can have, or at least we can suppose, an impression which is recognized without being localized ; but if it is localized this means that a more complex presentation is formed by the addition of new elements, not that a second distinct object is presented and some indescribable connexion established between the impression and it, still less that the impression is referred to something not strictly presented at all. The truth is that the body as extended is from the psychological point of view not perceived at all apart from localized impressions. In like manner impressions projected (or the absence of impressions projected) constitute al that is perceived as the occupied (or un-occupied) space beyond. It is not till a much later stage, after many varying experiences of different impressions similarly localized or projected, that even the mere materials are present for the formation of such an abstract conception of space as "spatial reference" implies. Psychologists, being themselves at this later stage, are apt to commit the oversight of introducing it into the earlier stage of which they have to expound.
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