For these, we must return to the distinction loosely established above, between passive and active assimilation. We know that the fundamental mechanism of cognition may be reduced to two antagonistic processes, association and dissociation, assimilation and dissimilation; to combine, to separate; in brief, analysis and synthesis.[71] In the formation of the generic image, as we have seen, assimilation plays the principal part; the mind works only upon similarities. In proportion as we recede from this point, we have the contrary; the mind works more and more upon differences; the primitive and essential operation is a dissociation; the fusion of similarities only appears later. The further back we go, the more analysis preponderates, because we are pursuing resemblances more and more hidden by differences. Coarser minds do not rise above palpable similarities. The peasant who hears a dialect or patois closely akin to his own understands nothing of it; it is another language to him; whereas even a mediocre linguist immediately perceives the identity of words that differ only in accent. We may represent the differences between generic images, and these general notions that most nearly approximate to them, by the following symbol: I. _A B C d e_ _A B C e f_ _A B C g h_, etc. II. _A b c d e_ _x y z A f_ _g A h k m_, etc. where each line corresponds to an object, and each letter to one of the principal characters of the object. Table I is that of the generic image. A part, _A B C_, is constantly repeated in each experience; moreover, it is in relief, as indicated by the capitals; the elimination of differences is almost passive,—self-caused; they are forgotten. Table II is that of a fairly simple general notion. Here _A_ has to be disengaged from all the objects in which it is included. It still has a salient character, indicated by capitals, and recurring in each object; but as it is merged in the differences, as it represents but a poor fraction of the total event, it is not disengaged spontaneously; it exacts a preliminary labor of dissociation and elimination. Thus understood, the difference between the two processes consists only in the faculty of greater or less dissociation, and we are in no way authorised in assuming a difference of nature.