Page:The System of Nature.djvu/74

 wills, their actions, have eternally for their object and their end. This self-gravitation, then, is clearly a necessary disposition in man, and in all other beings; which, by a variety means, contribute to the preservation of the existence they have received, as long as nothing deranges the order of their machine, or its primitive tendency.

Cause always produces effect; there can be no effect without cause. Impulse is always followed by some motion, more or less sensible; by some change, more or less remarkable in the body which receives it. But motion, and its various modes of displaying itself, is, as has been already shewn, determined by the nature, the essence, the properties, the combinations of the beings acting. It must, then, be concluded that motion, or the modes by which beings act, arises from some cause; that as this cause is not able to move or act, but in conformity with the manner of its being or its essential properties, it must equally be concluded, that all the phenomena we perceive are necessary; that every being in Nature, under the circumstances in which it is placed, and with the given properties it possesses, cannot act otherwise than it does.

Necessity is the constant and infallible relation of causes with their effects. Fire consumes, of necessity, combustible matter plated within its circuit of action: man, by fatality, desires either that which really is, or appears to be serviceable to his welfare. Nature, in all the extraordinary appearances she exhibits, necessarily acts after her own peculiar essence: all the beings she contains, necessarily act each after its own a individual nature: it is by motion that the whole has relation with its parts; and these