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present to reinstate the past impressions of the same thing, we restrict ourselves to those cases where the reinstatement is sure and certain, in fact to cases of absolute identity of the present and past. Such is the nature of the instances dwelt upon in the previous chapter: in all of them, the new movement, or the new image, was supposed precisely identical with the old, and went simply to reinstate and to deepen an impression already made. We must, however, now pass beyond this field of examples, and enter upon a new class where the identity is only partial, and is on that account liable to be missed; where the restoration, instead of being sure, is doubtful; and where, moreover, the reinstatement serves higher purposes than the mere iteration and deepening of the impression already made. In all mental restorations whatsoever, both Contiguity and Similarity are at work; in one class, the question is as to the sufficiency of the contiguous bond, the similarity being sure; in another class, the question is as to the sufficiency of the attractive force of the likeness, the contiguous adhesiveness being believed certain. If I chance to meet with a person I have formerly seen, and endeavour to remember his name, it will depend upon the goodness of a cohesive link whether or not I succeed; there will be no difficulty in my recalling the past impression of his personal appearance through the force of the present impression; but having recalled the full total of the past impressions, I may not be able to recover the accompaniment of the name; the contiguity may be at fault, although the similarity works its perfect work of restoring to me my previous conception of the personal aspect. If, on the other hand, I see a man on the street, and if I have formerly seen a portrait of that man, it is a question whether the living reality shall recall the portrait; the doubt hangs not upon the contiguity, or coherence of the parts and surroundings of the picture, if it could be recovered, but upon the chance of its being recovered. Where things are identical, the operation of similarity, in making the present case revive the former ones, is so certain that it is not even mentioned; we

talk of the goodness of the cohesive bond between the revived part and its accompaniments, as if contiguity expressed the whole fact of the restoration. To make up for this partiality of view, which was indispensable to a clear exposition, we now embrace, with the like partial and prominent consideration, the element that was left in a latent condition; and allow to sink, into the latent state, the one 'that has hitherto been made exclusively prominent.*

3. In the perfect identity between a present and a past impression, the past is recovered and fused with the present, instantaneously and surely. So quick and unfaltering is the process that we lose sight of it altogether; we are scarcely made aware of the existence of an associating link of similarity in the chain of sequence. When I look at the full moon, I am instantly impressed with the state arising from all my former impressions of her disc added together; so natural and necessary does this restoration seem, that we rarely reflect on the principle implied in it, namely, the power of the new stimulus to set on the nervous currents, with all the energy acquired in the course of many hundred repetitions of the same visual impetus. But when we pass from perfect to imperfect or partial identity, we are more readily made aware of the existence of this link of attraction between similars, for we find that sometimes the restoration does not take place; cases occur where we fail to be struck with a similitude; the spark does not pass between the new currents and the old dormant ones. The failure in reinstating the old condition by virtue of the present stimulus, is, in the main, ascribable to imperfect identity. When, in some new impression of a thing, the original form is muffled, obscured, distorted, disguised, or in any way altered, it is a chance whether or not we identify it; the amount of likeness that remains will have a reviving power, or a

* To a mathematical student this would be made at once intelligible by saying that, in the former chapter, the Contiguity is assumed as the variable element, and the Similarity the constant; in this chapter, Similarity is supposed variable and Contiguity constant.

OBSTRUCTIVES TO THE REVIVING POWER OF SIMILARITY. 461

certain amount of reinstating energy, but the points of difference or unlikeness will operate to resist the supervention of the old state, and will tend to revive objects like themselves. If I hear a musical air that I have been accustomed to, the new impression revives the old as a matter of course; but if the air is played with complex harmonies and accompaniments, it is possible that the effect of these additions may be to check my recognition of the piece; the unlike circumstances may repel the reinstatement of the old experience more powerfully than the remaining likeness attracts it; and I may find in it no identity whatever with an air previously known, or even identify it with something altogether different. If my hold of the essential character of the melody is but feeble, and if I am stunned and confounded with the new accompaniments, there is every likelihood that I shall not experience the restoration of my past hearing of the air intended, and consequently I shall not identify the performance.

4. The obstructives to the revival of the past through similitude, may be classed under the two heads-Faintness and Diversity. There are instances where a new impression is too feeble to strike into the old-established track of the same impression, and to make it alive again; as when we are unable to identify the taste of a very weak solution, or to discern an object in twilight dimness. The most numerous and interesting cases come, however, under the other headDiversity, or mingled likeness and unlikeness; as when we meet an old acquaintance in a new dress, or in circumstances where we have never seen the same person before. The modes of diversity are countless, and incapable of being classified. We might, indeed, include under diversity the other of the two heads, seeing that faintness implies diversity of degree, if not of any other circumstance; but I prefer considering the obstruction arising from faintness by itself, after which we shall proceed to the larger field of examples marked by unlikeness in other respects.

5. The difficulty or facility in resuming a past mental

condition, at the suggestion of a present similitude, will plainly depend upon the hold that the past impression has acquired; it is much easier to revive a familiar image than an unfamiliar, by the force of a new presentation. We shall, therefore, have to keep this circumstance in view, among others, in the course of our illustration of the law of Similarity.

It has to be considered how far natural character-that is, a primitive endowment of the intellect, enters into the power of reviving similars, or of bringing together like things. in spite of the repulsion of unlike accompaniments. There is much to be explained in the preferences shown by dif ferent minds, in the objects that they most readily recall to the present view; which preferences determine varieties of character, such as the scientific and the artistic minds. The explanation of these differences was carried up to a certain point under the Law of Contiguity; but, if I am not mistaken, there is still a portion referable to the existence of various modes and degrees of susceptibility to the force of Similarity. From all that I have been able to observe, the two energies of contiguous adhesion, and of attraction of similars, do not rise and fall together in the character; we may have one feeble and the other strong, in all proportions and degrees of adjustment. I believe, moreover, that there is such a thing as an energetic power of recognizing similarity in general, and that this is productive of remarkable consequences. Whether I shall be able to impress these convictions upon my readers, will depend upon the success of the detailed exposition of this noted peculiarity of our intellectual nature.

FEEBLENESS OF IMPRESSION.

6. We commence with the case of Faintness, or Feebleness, in the present, or suggesting impression, considered as an obstacle to the revival of the corresponding previous impression. There is, in every instance, a certain degree of feebleness that will disable the present image from falling

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into the track left by the same image in its former advent. When an extremely faint influence, in the present, revives the old currents, we must suppose the restoring action of similarity to be unusually vigorous in that mind, or for that class of impressions. Thus, if from a very feeble solution of salt in water, such as occurs in many land springs, the impression on the tongue were sufficient to revive in one person, and not in another, the past state of mind produced by the tasting of salt, we should naturally remark that the one excelled the other in the attractive force of similarity so far as concerned Taste. The superiority, however, admits of being referred to various circumstances. (1.) In the first place, mere natural acuteness of taste, such as is shown in nicety of discrimination, would also show itself in greater readiness to identify a feeble impression. (2.) In the next place, there might be a greater previous familiarity with this particular taste, the consequence of repetition and the other circumstances favouring retentiveness. (3.) Distinct from the last, although apt to concur with it, is the habit of concentrating the attention upon the sense of taste, owing to some special interest or motive. These are three circumstances having a special or local reference, and not implying greater power of Similarity on the whole; but we shall find reason for believing, on grounds analogous to those brought forward in support of a general power of retentiveness, that persons may differ as regards Similarity in general. If so, this is a fourth alternative explanation in the case supposed.

7. Such is an example taken at random, to show what is meant by the revival of impressions under the impediment of feebleness. I might go systematically through the Sensations of the various Senses, to gather illustrations of the same fact. (Movements apart from Sensations hardly furnish cases in point.) In the various sensations of Organic Life, there occur examples of difficult reinstatement, through feebleness of the suggesting sensation. I may experience a certain uneasy sensation, which I cannot describe or identify,