When the instinct of nature is excited, it is accompanied just as the heart in its moral emotions is, by certain movements of the body, which sometimes go before the will, sometimes, even as movements purely sympathetic, escape altogether its empire. In fact, as neither sensation, nor the desire, nor aversion, are subject to the free arbitration of man, man has no right over the physical movements which immediately depend on it. But the instinct does not confine itself to simple desire; it presses, it advances, it endeavors to realize its object; and if it does not meet in the autonomy of the mind an energetic resistance, it will even anticipate it, it will itself take the initiative of those sorts of acts over which the will alone has the right to pronounce. For the instinct of conservation tends without ceasing to usurp the legislative powers in the domain of the will, and its efforts go to exercise over man a domination as absolute as over the beast. There are, then, two sorts of distinct movements, which, in themselves and by their origin, in each affective phenomenon, arise in man by the instinct of conservation: those firstly which immediately proceed from sensation, and which, consequently, are quite involuntary; then those which in principle could and would be voluntary, but from which the blind instinct of nature takes all freedom. The first refer to the affection itself, and are united necessarily with it; the others respond rather to the cause and to the object of the affections, and are thus accidental and susceptible of modification, and cannot be mistaken for infallible signs of the affective phenomena. But as both one and the other, when once the object is determined, are equally necessary to the instinct of nature, so they assist, both one and the other, the expression of affective phenomena; a necessary competition, in order that the expression should be complete and form a harmonious whole.