Sorrow rightly belongs in the category of depressing emotions, and yet, it has as great influence on invention as any other emotion. Do we not know that melancholy and even profound sorrow has furnished poets, musicians, painters, and sculptors with their most beautiful inspirations? Is there not an art frankly and deliberately pessimistic? And this influence is not at all limited to esthetic creation. Dare we hold that hypochondria and insanity following upon the delirium of persecution are devoid of imagination? Their morbid character is, on the contrary, the well whence strange inventions incessantly bubble. Lastly, that complex emotion termed "self-feeling," which reduces itself finally to the pleasure of asserting our power and of feeling its expansion, or to the pitiable feeling of our shackled, enfeebled power, leads us directly to the motor elements that are the fundamental conditions of invention. Above all, in this personal feeling, there is the satisfaction of being a causal factor, i.e., a creator, and every creator has a consciousness of his superiority over non-creators. However petty his invention, it confers upon him a superiority over those who have invented nothing. Although we have been surfeited with the repeated statement that the characteristic mark of esthetic creation is "being disinterested," it must be recognized, as Groos has so truly remarked,[13] that the artist does not create out of the simple pleasure of creating, but in order that he may behold a mastery over other minds.[14] Production is the natural extension of "self-feeling," and the accompanying pleasure is the pleasure of conquest. Thus, on condition that we extend "imagination" to its full sense, without limiting it unduly to esthetics, there is, among the many forms of the emotional life, not one that may not stimulate invention. It remains to see this emotional factor at work,--to note how it can give rise to new combinations; and this brings us to the association of ideas. II We have said above that the ideal and theoretic law of the recurrence of images is that of "total redintegration," as e.g., recalling all the incidents of a long voyage in chronological order, with neither additions nor omissions. But this formula expresses what ought to be, not what actually occurs. It supposes man reduced to a state of pure intelligence, and sheltered from all disturbing influences. It suits the completely systematized forms of memory, hardened into routine and habit; but, outside of these cases, it remains an abstract concept.