With the image, the intermediate stage between percept and concept, the reduction of the object represented to a few fundamental features is still more marked. Not merely is there among the different representations which I may have of some man, dog, or tree, one that for the time being necessarily excludes the others (my oak tree perforce appears to me in summer foliage, tinted by autumn, or bereft of leaves,—in bright light or in shade), but even this individual, concrete representation which prevails over the others is no more than a sketch, a reduction of reality with many details omitted. Apart from the exceptionally gifted men in whom mental vision and mental audition are perfect, and wholly commensurate (as it would seem) with perception, the representations which we call exact are never so, except in their most general features. Compare the image we have with our eyes closed of a monument, with the perception of the monument itself; the remembrance of a melody with its vocal or instrumental execution. In the average man, the image, the would-be copy of reality invariably suffers a conspicuous impoverishment, which is enormous in the less lavishly endowed; it is here reduced to a mere schema, limited to the inferior concepts.
Doubtless it may be objected that the work of dissociation in perception and representation is incomplete and partial. It would be strange and illogical indeed if the abstract were to triumph in the very heart of the concrete; we do but submit that it is here in germ, in embryonic shape. And hence, when abstraction appears in its true form, as the consciousness of one unique quality isolated from the rest, it is no new manifestation but a fruition, it is a simplification of simplifications.
The state of consciousness thus attained, by the fixation of attention on one quality exclusively, and by its ideal dissociation from the rest, becomes, as we know, a notion which is neither individual nor general, but abstract,—and this is the material of generalisation.
The sense of identity, the power of apprehending resemblances, is, as has justly been said, “the keel and backbone of our thinking”; without it we should be lost in the incessant stream of things.[6] Are there in nature any complete resemblances, any absolutely similar events? It is extremely doubtful. It might be supposed that a person who reads a sentence several times in succession, who listens several times to the same air, who tastes all the four quarters of the same fruit, would experience in each case an identical perception. But this is not so. A little reflexion will show that besides differences in time, in the varying moods of the subject, and in the cumulative effect of repeated perceptions, there is at least between the first perception and the second, that radical difference which separates the new from the repeated. In fact, the material given us by external and internal experience consists of resemblances alloyed by differences which vary widely in degree,—in other words, analogies. The perfect resemblance assumed between things vanishes as we come to know them better. At first sight a new people exhibits to the traveller a well-determined general type; later, the more he observes, the more the apparent uniformity is resolved into varieties. “I have taken the trouble,” says Agassiz, “to compare thousands of individuals of the same species; in one case I pushed the comparison so far as to have placed side by side 27,000 specimens of one and the same shell (genus Neretina). I can assure you that in these 27,000 specimens I did not find two that were perfectly alike.”
Is this faculty of grasping resemblances—the substrate of generalization—primitive, in the absolute signification of the word? Does it mark the first awakening of the mind, in point of cognition? For several contemporary writers (Spencer, Bain, Schneider, and others) the consciousness of difference is the primordial factor; the consciousness of resemblance comes later. Others uphold the opposite contention.[7] As a matter of fact this quest for the primum cognitum is beyond our grasp; like all genetical questions, it eludes our observation and experience.
No conclusion can be formed save on purely logical arguments, and each side advances reasons that carry a certain weight. There is, moreover, at the bottom of the whole discussion, the grave error of identifying the embryonic state of the mind with its adult forms, and of presupposing a sharp initial distinction between discrimination and assimilation. The question must remain open, incapable of positive solution by our psychology. The incontestable truth with regard to the mind, as we know it in its developed and organised state, is that the two processes advance pari passu, and are reciprocally causative.
In sum, abstraction and generalisation considered as elementary acts of the mind, and reduced to their simplest conditions, involve two processes:
1. The former, abstraction, implies a dissociative process, operating on the raw data of experience. It has subjective causes which are ultimately reducible to attention. It has objective causes which may be due to the fact that a determinate quality is given us as an integral part of widely different groups.
“Any total impression whose elements are never experienced apart must be unanalysable. If all cold things were wet and all wet things cold, if all liquids were transparent and no non-liquid were transparent, we should scarcely discriminate between coldness and wetness and scarcely ever invent separate names for liquidity and transparency.... What is associated now with one thing and now with another tends to become dissociated from either, and to grow into an object of abstract contemplation by the mind. One might call this the law of dissociation by varying concomitants.”[8]
2. The latter, generalisation, originates in association by resemblance, but even in its lowest degree it rises beyond this, since it implies a synthetic act of fusion. It does not, in fact, consist in the successive excitation of similar or analogous percepts, as in the case where the image of St. Peter’s in Rome suggests to me that of St. Paul’s in London, of the Pantheon in Paris, and of other churches with enormous dimensions, of like architecture, and with gigantic domes. It is a condensation. The mind resembles a crucible with a precipitate of common resemblances at the bottom, while the differences have been volatilised. In proportion as we recede from this primitive and elementary form, the constitution of the general idea demands other psychological conditions which cannot be hastily enumerated.