The distinction between the two is not at all absolute. Every fixed idea is supported and maintained by a need, a tendency, a desire; i.e., by an affective element. For it is idle fancy to believe in the _persistence_ of an idea which, by hypothesis, would be a purely intellectual state, cold and dry. The principle of unity in this form naturally predominates in certain kinds of creation: in the practical imagination wherein the end is clear, where images are direct substitutes for things, where invention is subjected to strict conditions under penalty of visible and palpable check; in the scientific and metaphysical imagination, which works with concepts and is subject to the laws of rational logic. Every fixed emotion should realize itself in an idea or image that gives it body and systematizes it, without which it remains diffuse; and all affective states can take on this permanent form which makes a unified principle of them. The simple emotions (fear, love, joy, sorrow, etc.), the complex or derived emotions (religious, esthetic, intellectual ideas) may equally monopolize consciousness in their own interests. We thus see that these two terms--fixed idea, fixed emotion--are almost equivalent, for they both imply inseparable elements, and serve only to indicate the preponderance of one or the other element. This principle of unity, center of attraction and support of all the working of the creative imagination--that is, a subjective principle tending to become objectified--is the ideal. In the complete sense of the word--not restrained merely to esthetic creation or made synonymous with perfection as in ethics--the ideal is a construction in images that should become a reality. If we liken imaginative creation to physiological generation, the ideal is the ovum awaiting fertilization in order to begin its development. We could, to be more exact, make a distinction between the synthetic principle and the ideal conception which is a higher form of it. The fixation of an end and the discovery of appropriate means are the necessary and sufficient conditions for all invention. A creation, whatever it be, that looks only to present success, can satisfy itself with a unifying principle that renders it viable and organized, but we can look higher than the merely necessary and sufficient. The ideal is the principle of unity in motion in its historic evolution; like all development, it advances or recedes according to the times. Nothing is less justified than the conception of a fixed archetype (an undisguised survival of the Platonic Ideas), illuminating the inventor, who reproduces it as best he can. The ideal is a nonentity; it arises in the inventor and through him; its life is a _becoming_.