Let us consider first the class of non-esthetic creations. Very different in nature, all the products of this group coincide at one point:--they are of practical utility, they are born of a vital need, of one of the conditions of man's existence. There are first the inventions "practical" in the narrow sense--all that pertains to food, clothing, defense, housing, etc. Every one of these special needs has stimulated inventions adapted to a special end. Inventions in the social and political order answer to the conditions of collective existence; they arise from the necessity of maintaining the coherence of the social aggregate and of defending it against inimical groups. The work of the imagination whence have arisen the myths, religious conceptions, and the first attempts at a scientific explanation may seem at first disinterested and foreign to practical life. This is an erroneous supposition. Man, face to face with the higher powers of nature, the mystery of which he does not penetrate, has a _need_ of acting upon it; he tries to conciliate them, even to turn them to his service by magic rites and operations. _His_ curiosity is not at all theoretic; he does not aim to know for the sake of knowing, but in order to act upon the outside world and to draw profit therefrom. To the numerous questions that necessity puts to him his imagination alone responds, because his reason is shifting and his scientific knowledge _nil_. Here, then, invention again results from urgent needs. Indeed, in the course of the nineteenth century and on account of growing civilization all these creations reach a second moment when their origin is hidden. Most of our mechanical, industrial and commercial inventions are not stimulated by the immediate necessity of living, by an urgent need; it is not a question of existence but of better existence. The same holds true of social and political inventions which arise from the increasing complexity and the new requirements of the aggregates forming great states. Lastly, it is certain that primitive curiosity has partially lost its utilitarian character in order to become, in some men at least, the taste for pure research--theoretical, speculative, disinterested. But all this in no way affects our thesis, for it is a well-known elementary psychological law that upon primitive wants are grafted acquired wants fully as imperative. The primitive need is modified, metamorphosed, adapted; there remains of it, nonetheless, the fundamental activity toward creation.