1902 Encyclopedia > Psychology > Psychological Law of Relativity

(Part 22)

(C) Theory of Presentations (cont.)

Psychological Law of Relativity

This will be the most convenient place to take note of certain psychological doctrines which, though differing in some material respects, are usually included under the term Law of Relativity.

Hobbes’s Idem semper sentire et non sentire ad idem recidunt is often cited as one of the first formulations of this law ; and if we take it to apply to the whole field of consciousness it becomes at once true and trite : a field of consciousness unaltered either by change of impression or of ideas would certainly be a blank and a contradiction. Understood in this sense the Law of Relativity amounts to what Hamilton called the Law of Variety (Reid’s Works, p. 932). But, though consciousness involves change, it is still possible that particular presentations in the field of consciousness may continue unchanged indefinitely. When it is said that "a constant impression is the same as a blank," what is meant turns out to be something not psychological at all, as, e.g., our insensibility to the motion of the earth or to the pressure of the air—cases in which there is obviously no presentation, nor even any evidence of nervous change. Or else this paradox proves to be but an awkward way of expressing what we may call accommodation, whether physiological or psychological. Thus the skin soon adapts itself to certain seasonal alternations of temperature, so that heat or cold ceases to be felt : the sensation because the nervous change, its proximate physical counterpart, has ceased. Again, there is what James Mill calls "an acquired incapacity of attention," such that a constant noise, for example, in which we have no interest is soon inaudible. As attention moves away from a presentation its intensity diminishes, and when the presentation is below the threshold of consciousness its intensity is then subliminal, whatever that of the physical stimulus may be. In such a case of psychological accomodation we should expect also to find on the physiological side some form of central reflexion or isolation more or less complete. As a rule, no doubt, impressions do not continue constant for more than a very short time; still there are sad instances enough in the history of disease, bodily and mental, to show that such a thing can quite well happen, and that such constant impressions (and "fixed ideas," which are in effect tantamount to them), instead of becoming blanks, may dominate the entire consciousness, colouring or bewildering everything.

From the fact that the field of consciousness is continually changing it has been supposed to follow, not only that a constant presentation is impossible, but as a further consequence that every presentation is essentially nothing but a transition or difference. "All feeling," says Dr Bain the leading exponent of this view, "is two-sided…. We may attend more to one member of the couple than to the other….We are more conscious of heat when passing to a higher temperature, and of cold when passing to a lower. The state we have passed to is our explicit consciousness, the state we have passed from is our implicit consciousness." But the transition need not be from heat to cold, or vice versa: it can equally well take place from a neutral state, which is indeed the normal state, of neither heat nor cold ; a new-born mammal, e.g., must experience cold, having never experienced heat. Again, suppose a sailor becalmed, gazing for a whole morning upon a stretch of sea and sky sensations are implicit here? Shall we say yellow as the greatest contrast to blue, or darkness as the contrary of light, or both? What, again, is the implicit consciousness when the explicit is sweet; is it bitter or sour, and from what is the transition in such a case?

It is different to avoid suspecting a certain confusion here between the transition of attention from one presentation to another and the qualitative differences among presentations themselves. It is strange that the psychologist who has laid such stress on neutral states of surprise as being akin to feeling, and so distinct from special presentations, should in any way confound the two. The mistake, if mistake indeed it be, is perhaps accounted for by the fact that Dr Bain, in common with the rest of his school, nowhere distinguishes between attention and the presentations that are attended to. To be conscious or mentally alive we must have a succession of shocks or surprises, new objects calling off attention from old ones; but, over and above these movements of attention from presentation to presentation, do we find that each presentation is also itself but a transition or difference? "We do not know any one thing of itself but only the difference between it and another thing," says Dr Bain. But it is plain we cannot speak of contrast or difference between two states or things as a contrast or difference if the states or things are not themselves presented, else the so-called contrast or difference would itself be a single presentation, and its supposed "relativity" but an influence. Difference is not more necessary to the presentation of two objects to the presentation of difference. And, what is more, a difference between presentation is not at all same thing as the presentation of the difference. The former must precede the latter ; the latter, which requires active comparison, need not follow. There is an ambiguity in the words "know," "knowledge," which Dr Bain seems not to have considered: "to know" may mean either to perceive or apprehend, or it may mean to understand or comprehend. [Footnote 49-1] Knowledge in the first sense is only what we shall have presently to discuss as the recognition or assimilation of an impression (see below, p. 53) ; knowledge in the latter sense is the result of intellectual comparison and is embodied in a proposition. Thus a blind man who cannot know light in the first sense can know about light in the second if he studies a treatise on optics. Now in simple perception or recognition we cannot with any exactness say that two things are perceived : straight is a thing, i.e., a definite object presented ; not so not-straight, which may be qualitatively obscure or intensively feeble to any degree. Only when we rise to intellectual knowledge is it true to say, "No one could understand the meaning of a straight without being shown a line not straight, a bent or crooked line." [Footnote 49-2] Two distinct presentations are necessary to the comparison that is here implied; but we cannot begin with such definitional differentiation : we must fist recognize our objects before we can compare them. We need then, to distinguish between the comparativity of intellectual knowledge, which we must admit—for it rests at bottom on a purely analytical proposition—and the "differential theory of presentations," which, however plausible at first sight, must be wrong somewhere since it commits us to absurdities. Thus, if we cannot have a presentation X but only the presentation of the difference between Y and Z, it would seem that in like manner we cannot have presentation of Y or Z, nor therefore of their difference X, till we have had the presentation of A and B say, which differ by Y, and of C and D, which we may suppose differ Z. The lurking error in this doctrine, that all presentations are but differences, may perhaps emerge if we examine more closely what may be meant by difference. We may speak of (a) difference in intensity between sensations supposed to be qualitatively identical, or of (b) differences in quality in the same continuum or class of presentations, or of (c) differences between of different classes or continua. Now, as regards (a) and (b), it will be found that the difference between two intensities of the same quality, or between two qualities of the same continuum, may be itself a distinct presentation. But nothing of this kind holds of (c). [Footnote 50-1] In passing from a load of 10 lb to one of 20 lb, or from the sound of a note to that of its octave, it is possible to make the change continuously, and to estimate it as one might the distance between two places on the same road. But in passing from the scent of a rose to the sound of a going or a sting from a bee we have no such means of bring the two into relation—scarcely more than we might have of measuring the length of a journey made partly on the common earth and partly through the looking-glass. In (c), then, we have only a change, a difference of presentation, but not a presentation of difference ; and only have more than this in (a) or (b) provided the selected presentations occur together. If red follows green we may be aware of a greater difference than we could if red followed orange ; and we should ordinarily call a 10-lb load heavy after one of 5 lb and light after one of 20 lb. Facts like these it is which make the differential theory of presentations plausible.

On the strength of such facts Wundt has formulated a law of relatively, free, apparently, from the objections just urged against Dr Bain’s doctrine, which runs thus : --"Our sensations afford no absolute but only a relative measure of external impression. The intensities of stimuli, the pitch of tones, the qualities of light, we apprehend (empfinden) in general only according to their mutual relation, not according to any unalterably fixed unit given along with or before the impression itself." [Footnote 50-2] We are not now concerned with so much of his statement as relates to the physical antecedents of sensation : but that what is of psychological account in it requires very substantial qualification is evident at once from a single consideration, viz., that if true this law would make it quite immaterial what the impressions themselves, were : provided the relation continued the same, the sensation would be the same too, just as the ratio of 2 to 1 is the same whether our unit be miles or millimètres. IN the case of intensities , e.g., there is a minimum sensibile and a maximum sensibile. The existence of such extremes is alone sufficient to turn the flank of the thoroughgoing relativists ; but there are instances enough of intermediate intensities that are directly recognized. A letter-sorter, for example, who identifies an ounce or two ounces with remarkable exactness identifies each for itself and not first as half the second ; of an ounce and a half or of three ounces he may have a comparatively vague idea. And so generally within certain limit of error, indirectly ascertained, we can identify intensities, each for itself, neither referring to a common standard nor to one that varies from time to time—to any intensity, that is to say, that chances to be simultaneously presented; just as an enlisting sergeant will recognize a man fit for the Guards without a yard measure and whether the man’s comrades are tall or short. Of course such identification is only possible through the reproduction of past impressions, but then such reproduction itself is only possible because the several impressions concerned have all along had a certain independence of related impressions, and a certain identity among themselves. As regards the qualities of sensations the outlook of the relativist is, if anything, worse. In what is called Meyer’s experiment, e.g. (described under EYE, vol. vii. P. 825), what appears greenish on a red ground will appear of an orange tint on a ground of blue ; but this contrast is only possible within certain very narrow limits. In fact, the phenomena of colour-contrast, so far from proving, distinctly disprove that we apprehend the qualities of light only according to their mutual relation. In the case of tones it is very questionable whether such contrast exist at all. Summing up on the particular doctrine of relativity of which Wundt is the most distinguished adherent, the truth seems to be that, in some cases where two presentations whose difference is itself presentable occur in close connexion, this difference—as we indirectly learn—exerts a certain bias on the assimilation or identification of one or both of the presentations. There is no "unalterably fixed unit’ certainly, but, on the other hand, "the mutual relations of impressions" are not everything. [Footnote 50-3]


49-1 Other languages give more prominence to this distinction; compare gnonai [Gk.] and eidenai [Gk.] and noscere [Lat.] and scire [Lat.], kennen [Ger.] and wissen [Ger.], connaître [Fr.] and savoir [Fr.]. On this subject there are some acute remarks in a little-known book, the Exploratio Philosophica, of Professor J. Grote. Hobbes too was well awake to this difference, as, e.g., when he says, "There are two kinds of knowledge; the one, sense or knowledge original and remembrance of the same; the other, science or knowledge of the truth of propositions, derived from understanding."

49-2 Bain, Logic, vol. i. p. 3.

50-1 Common language seems to recognize some connexion even here, or we should not speak of harsh tastes and harsh sounds, or of dull sounds and dull colours, and so forth. All this is, however, super-added to the sensation, probably on the ground of similarities in the accompanying organic sensations.

50-2 Physiologische Psychologie, 1st ed., p. 421; the doctrine re-appears in the 2nd ed., but no equally general statement of it is given.

50-3 Those who, like Helmholtz, explain the phenomena of contrast and the like as illusions of judgment, must class them as cases of comparativity ; those who, like Hering, explain them physiologically , would see in them nothing but physiological adaptation.

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