Now, Rëaction, as far as we know anything of it, is Action conversed. The _general_ principle of Gravity being, in the first place, understood as the rëaction of an act—as the expression of a desire on the part of Matter, while existing in a state of diffusion, to return into the Unity whence it was diffused; and, in the second place, the mind being called upon to determine the _character_ of the desire—the manner in which it would, naturally, be manifested; in other words, being called upon to conceive a probable law, or _modus operandi_, for the return; could not well help arriving at the conclusion that this law of return would be precisely the converse of the law of departure. That such would be the case, any one, at least, would be abundantly justified in taking for granted, until such time as some person should suggest something like a plausible reason why it should _not_ be the case—until such period as a law of return shall be imagined which the intellect can consider as preferable. Matter, then, irradiated into space with a force varying as the squares of the distances, might, _à priori_, be supposed to return towards its centre of irradiation with a force varying _inversely_ as the squares of the distances: and I have already shown[3] that any principle which will explain why the atoms should tend, according to any law, to the general centre, must be admitted as satisfactorily explaining, at the same time, why, according to the same law, they should tend each to each. For, in fact, the tendency to the general centre is not to a centre as such, but because of its being a point in tending towards which each atom tends most directly to its real and essential centre, _Unity_—the absolute and final Union of all. [3] Page 44. The consideration here involved presents to my own mind no embarrassment whatever—but this fact does not blind me to the possibility of its being obscure to those who may have been less in the habit of dealing with abstractions:—and, upon the whole, it may be as well to look at the matter from one or two other points of view.