Before we embark on the study of the principal concepts, it is incumbent upon us (in order to determine for each of these, separately, the conditions of their genesis and development—as was shown for abstraction in general) to throw as much light as possible upon the very vexed question of the psychological nature of the concepts of pure symbolism, where the word appears as the sole element that exists in consciousness. Is it true that we can think effectually and usefully with words and nothing but words, as has been sustained to satiety? Is not this assertion founded upon the misapprehension of a factor which, although it does not enter into consciousness, is none the less in active existence? The investigation of this point is the prime object of the following chapter. It is unnecessary to enter in detail into the researches of the last thirty years, as to the seat and the nature of images. Yet since these have been the point of departure of the following inquiry, the results may be briefly summarised. It is generally admitted that the image occupies the same seat as the percept of which it is a weak and incomplete residuum, i. e., in order to produce itself in consciousness it demands the putting into activity of certain definite portions of the cerebral centres. The energy of the representative faculty does not merely vary from individual to individual in a general manner: there are particular forms of imagination, constituted by the very marked predominance of a certain group of representations, visual, auditory, muscular, olfactory, gustatory. Normal observation, and still more pathological documents, have thus determined certain types. We may also (though this is mere hypothesis and difficult to verify) admit a “mixed” or “indifferent” type, in which the different species of sensations are represented by corresponding images of equal clearness and vigor, without marked predominance of any one group, whilst still maintaining their relative importance: e. g., it is clear that in man the visual and olfactory images cannot be equivalent in absolute importance. Excluding this indifferent type, we have three principal “pure” types: visual, auditory, muscular or motor, signifying a tendency to represent things in terms borrowed from vision, from sound, or from movement. If we push the investigation further, we find that these types again imply variations or sub-types. Thus there may be a lively faculty for representation of complex visual forms (faces, landscapes, monuments) along with a weak sense for graphic signs (printed or written words) and so on. The numerous works devoted to this subject, and too well known to be insisted on here, lead us to this conclusion: that there is no general faculty of imagination. This is a vague term which designates very different individual variations; these last alone have any psychological reality, and are alone important in cognising the mechanism of the intellect.