It would seem, at first sight, that the first and third suppositions involve impossibilities, and that the second, therefore, is the only one which we are at liberty to adopt. As regards the first, it may be said—How can we have a feeling without feeling it, in other words, without being conscious of it? With regard to the third, how, it may be asked, can any link of the chain have been altogether absent, through the pressure of the subsequent links? The subsequent ideas are only there because called up by it, and would not have arisen at all unless it had arisen first, however short a time it may have lasted. These arguments seem strong, but are not so strong as they seem.
In favour of the first supposition, that feelings may be unconsciously present, various facts and arguments are adduced by Sir William Hamilton in his Lectures; but I think I have shewn in another work, that the arguments are inconclusive, and the facts equally reconcilable with the second of the three hypotheses. That a feeling should not be felt appears to me a contradiction both in words and in nature. But, though a feeling cannot exist without being felt, the organic state which is the antecedent of it may exist, and the feeling itself not follow. This happens, either if the organic state is not of sufficient duration, or if an organic state stronger than itself, and conflicting with it, is affecting us at the same moment. I hope to be excused for quoting what I have said elsewhere on this subject (Examination of Sir William Hamilton’s Philosophy, ch. 15).
“In the case, for instance, of a soldier who receives a wound in battle, but in the excitement of the moment is not aware of the fact, it is difficult not to believe that if the wound had been accompanied by the usual sensation, so vivid a feeling would have forced itself to be attended to and remembered. The supposition which seems most probable is, that the nerves of the particular part were affected as they would have been by the same cause in any other circumstances, but that, the nervous centres being intensely occupied with other impressions, the affection of the local nerves did not reach them, and no sensation was excited. In like manner, if we admit (what physiology is rendering more and more probable) that our mental feelings, as well as our sensations, have for their physical antecedents particular states of the nerves; it may well be believed that the apparently suppressed links in a chain of association, those which Sir William Hamilton considers as latent, really are so; that they are not, even momentarily, felt; the chain of causation being continued only physically, by one organic state of the nerves succeeding another so rapidly that the state of mental consciousness appropriate to each is not produced. We have only to suppose, either that a nervous modification of too short duration does not produce any sensation or mental feeling at all, or that the rapid succession of different nervous modifications makes the feelings produced by them interfere with each other, and become confounded in one mass. The former of these suppositions is extremely probable, while of the truth of the latter we have positive proof. An example of it is the experiment which Sir W. Hamilton quoted from Mr. Mill, and which had been noticed before either of them by Hartley. It is known that the seven prismatic colours, combined in certain proportions, produce the white light of the solar ray. Now, if the seven colours are painted on spaces bearing the same proportion to one another as in the solar spectrum, and the coloured surface so produced is passed rapidly before the eyes, as by the turning of a wheel, the whole is seen as white. The physiological explanation of this phenomenon may be deduced from another common experiment. If a lighted torch, or a bar heated to luminousness, is waved rapidly before the eye, the appearance produced is that of a ribbon of light; which is universally understood to prove that the visual sensation persists for a certain short time after its cause has ceased. Now, if this happens with a single colour, it will happen with a series of colours: and if the wheel on which the prismatic colours have been painted, is turned with the same rapidity with which the torch was waved, each of the seven sensations of colour will last long enough to be contemporaneous with all the others, and they will naturally produce by their combination the same colour as if they had, from the beginning, been excited simultaneously. If anything similar to this obtains in our consciousness generally (and that it obtains in many cases of consciousness there can be no doubt) it will follow that whenever the organic modifications of our nervous fibres succeed one another at an interval shorter than the duration of the sensations or other feelings corresponding to them, those sensations or feelings will, so to speak, overlap one another, and becoming simultaneous instead of successive, will blend into a state of feeling, probably as unlike the elements out of which it is engendered, as the colour white is unlike the prismatic colours. And this may be the source of many of those states of internal or mental feeling which we cannot distinctly refer to a prototype in experience, our experience only supplying the elements from which, by this kind of mental chemistry, they are composed. The elementary feelings may then be said to be latently present, or to be present but not in consciousness. The truth, however, is that the feelings themselves are not present, consciously or latently, but that the nervous modifications which are their usual antecedents have been present, while the consequents have been frustrated, and another consequent has been produced instead.”
In this modified form, therefore, the first of the three hypotheses may possibly be true. Let us now consider the third, that of the entire elision of some of the ideas which form the associated train. This supposition seemed to be inadmissible, because the loss of any link would, it was supposed, cause the chain itself to break off at that point. To make the hypothesis possible, it is only, however, necessary to suppose, that, while the association is acquiring the promptitude and rapidity which it ultimately attains, each of the successive ideas abides for a brief interval in our consciousness after it has already called up the idea which is to succeed it. Each idea in the series, though introduced, not by synchronous, but by successive association, is thus, during a part of its continuance, synchronous with the idea which introduced it: and as the rapidity of the suggestions increases by still further repetition, an idea may become synchronous with another which was originally not even contiguous to it, but separated from it by an intervening link; or may come into immediate instead of mediate sequence with such an idea. When either of these states of things has continued for some time, a direct association of the synchronous or of the successive kind will be generated between two ideas which are not proximate links in the chain; A will acquire a direct power of exciting C, independently of the intervening idea B. If, then, B is much less interesting than C, and especially if B is of no importance at all in itself, but only by exciting C, and has therefore nothing to make the mind dwell on it after C has been reached, the association of A with C is likely to become stronger than that of A with B: C will be habitually excited directly by A; as the mind runs off to the further ideas suggested by C, B will cease to be excited at all; and the train of association, like a stream which breaking though its bank cuts off a bend in its course, will thenceforth flow in the direct line AC, omitting B. This supposition accounts more plausibly than either of the others for the truly wonderful rapidity of thought, since it does not make so large a demand as the other theories on our ability to believe that a prodigious number of different ideas can successively rush through the mind in an instant too short for measurement.
The result is, that all the three theories of this mental process seem to be quite possible; and it is not unlikely that each of them may be the real process in some cases, either in different persons, or in the same persons under different circumstances. I can only remit the question to future psychologists, who may be able to contrive crucial experiments for deciding among these various possibilities.—Ed.
106 11. Mr. Hume, and after him other philosophers, have said that our ideas are associated according to 107 three principles; Contiguity in time and place, Causation, and Resemblance. The Contiguity in time and 108 place, must mean, that of the sensations; and so far it is affirmed, that the order of the ideas follows that 109 of the sensations. Contiguity of two sensations in time, means the successive order. Contiguity of two 110 sensations in place, means the synchronous order. We have explained the mode in which ideas are associated, in the synchronous, as well as the successive order, and have traced the principle of contiguity to its proper source.
Causation, the second of Mr. Hume’s principles, is the same with contiguity in time, or the order of succession. Causation is only a name for the order established between an antecedent and a consequent; that is, the established or constant antecedence of the one, 111 and consequence of the other. Resemblance only remains, as an alleged principle of association, and it is necessary to inquire whether it is included in the laws which have been above expounded. I believe it will be found that we are accustomed to see like things together. When we see a tree, we generally see more trees than one; when we see an ox, we generally see more oxen than one; a sheep, more sheep than one; a man, more men than one. From this observation, I think, we may refer resemblance to the law of frequency, of which it seems to form only a particular case.[35]
[35] The reason assigned by the author for considering association by resemblance as a case of association by contiguity, is perhaps the least successful attempt at a generalisation and simplification of the laws of mental phenomena, to be found in the work. It ought to be remembered that the author, as the text shows, attached little importance to it. And perhaps, not thinking it important, he passed it over with a less amount of patient thought than he usually bestowed on his analyses.
Objects, he thinks, remind us of other objects resembling them, because we are accustomed to see like things together. But we are also accustomed to see like things separate. When two combinations incompatible with one another are both realised in familiar experience, it requires a very great preponderance of experience on one side to determine the association specially to either. We are also much accustomed to see unlike things together; I do not mean things contrasted, but simply unlike. Unlikeness, therefore, not amounting to contrast, ought to be as much a cause of association as likeness. Besides, the fact that when we see (for instance) a sheep, we usually see more sheep than one, may cause us, when we think of a sheep, to think of an entire flock; but it does not explain why, when we see a sheep with a black mark on its forehead, we are reminded of a sheep with a similar mark, formerly seen, though we never saw two such sheep together. It does not explain why a portrait makes us think of the original, or why a stranger whom we see for the first time reminds us of a person of similar appearance whom we saw many years ago. The law by which an object reminds us of similar objects which we have been used to see along with it, must be a different law from that by which it reminds us of similar objects which we have not been used to see along with it. But it is the same law by which it reminds us of dissimilar objects which we have been used to see along with it. The sight of a sheep, if it reminds us of a flock of sheep, probably by the same law of contiguity, reminds us of a meadow; but it must be by some other law that it reminds us of a single sheep previously seen, and of the occasion on which we saw that single sheep.
The attempt to resolve association by resemblance into association by contiguity must perforce be unsuccessful, inasmuch as there never could have been association by contiguity without a previous association by resemblance. Why does a sensation received this instant remind me of sensations which I formerly had (as we commonly say), along with it? I never had them along with this very sensation. I never had this sensation until now, and can never have it again. I had the former sensations in conjunction not with it, but with a sensation exactly like it. And my present sensation could not remind me of those former sensations unlike itself, unless by first reminding me of the sensation like itself, which really did coexist with them. There is thus a law of association anterior to, and presupposed by, the law of contiguity: namely, that a sensation tends to recall what is called the idea of itself, that is, the remembrance of a sensation like itself, if such has previously been experienced. This is implied in what we call recognising a sensation, as one which has been felt before; more correctly, as undistinguishably resembling one which has been felt before. The law in question was scientifically enunciated, and included, I believe for the first time, in the list of Laws of Association, by Sir William Hamilton, in one of the Dissertations appended to his edition of Reid: but the fact itself is recognised by the author of the Analysis, in various passages of his work; more especially in the second section of the fourteenth [chapter]. There is, therefore, a suggestion by resemblance—a calling up of the idea of a past sensation by a present sensation like it—which not only does not depend on association by contiguity, but is itself the foundation which association by contiguity requires for its support.