(C) Theory of Presentations (cont.)

Diffusion and Restriction. Incopresentability.

The importance of getting a firm grasp of this conception of a presentation-continuum as fundamental to the whole doctrine of presentations will justify us in ignoring a little longer the details of actual mental development and regarding it first from this more general point of view. In a given sensation, more particularly in our organic sensations, we can distinguish three variations, viz, variations of quality, of intensity, and of what Dr Bain has called massiveness, or, as we will say, extensity. This last characteristic, which everybody knows who knows the difference between the ache of a big bruise and the ache of a little one, between total and partial immersion in a bath, is, as we shall see later on, an essential element in our perception of space. But it is certainly not the whole of it, for in this experience of massive sensation alone it is impossible to find other elements which an analysis of special intuition unmistakably yields. Extensity and extension, then, are not to be confounded. Now we find, even at our level of mental evolution, that an increase in the intensity of a sensation is apt to entail an increase in its extensity too; this is still more apparent in the case of movements, and especially in the movements of the young. In like manner we observe a greater extent of movement in emotional expression when the intensity of the emotion increases. Even the higher region of imagination is no exception, as is shown by the whirl and confusion of ideas incident to delirium, and, indeed, to all strong excitement. But this "diffusion" or "radiation," as it has been called, diminished as we pass from the class of organic sensations of the five senses, from movements expressive of feeling to movements definitely purposive, and from the tumult of ideas excited by passion tot he steadier sequences determined by efforts to think. Increased differentiation seems, then, to be intimately connected with increased "restriction." The causal relations of the two must be largely matter of conjecture and cannot be fully discussed here. Probably there may be found certain initial differentiations which for psychology are ultimate facts that it cannot explain. But, such differentiations being given, then it may be safely said that, in accordance with what we have called the principle of subjective selection (see p. 42), attention would be voluntarily concentrated upon some of them and voluntary movements specially connected with these. To such subjectively initiated modifications of the presentation continuum, moreover, we may reasonably suppose "restriction" to be in large measure due. But increased restriction would render further differentiation of the given presentation possible and so the two processes might supplement each other. But, he their interaction what it may, these processes have now proceeded so far that at the level of human consciousness we find it hard to form any tolerably clear conception of a field of consciousness in which an intense sensation, no matter what, might diffuse over the whole. Colours, e.g., are with us so distinct from sounds that—except as regards the drain upon attetion—there is nothing in the intensest colour to affect the simultaneous presentation of a sound. But at the beginning whatever we regard as the earliest differentiation of sound might have been incopresentable with the earliest differentiation of colour, if sufficiently diffused, just as now a field of sight all blue is incopresentable with one all red. Or, if the stimuli appropriate to both were active together, the resulting sensation might have been what we should describe as a blending of the two, as purple is a blending or red and violet. Now, on the other hand, colours and sounds are necessarily so far localized that we are directly aware that the eye is concerned with the one and the ear with the other. This brings to our notice a fact so ridiculously obvious that it has never been deemed worthy of mention, and yet it has undeniably important bearings—the fat, viz., that certain sensation or movements are an absolute bar to the simultaneous presentation of other sensations or movements. We cannot see an orange at once yellow and green, though we can feel it at once as both smooth and cold ; we cannot open and close the same hand at the same moment, but we can open one hand while closing the other. Such incopresentability or contrariety is thus more than mere difference, and occurs only between presentations belonging to the same sense or to the same group of movements. Strictly speaking, it does not always occur even then ; for red and yellow, hot and cold, are presentable together provided they have certain other differences which we shall meet again presently as differences of local sign.





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