From our notion of simple elements we can form a very clear image of this being of reason. In a primitive element the matter borrows all its reality from the substantial form of which it is the intrinsic term--that is, from a virtual sphericity of which it is the centre. To change such a centre into a _pure_ potency of being, we have merely to suppress the virtual sphericity; for, by so doing, what was a _real_ centre of power becomes an _imaginary_ centre, a term deprived of its reality, a mere nothing; which however, from the nature of the process by which it is reached, is still conceived as the vestige of the real centre of power, and, so to say, the shadow of the real matter which disappears. Thus the _materia prima_, as a pure potency, is nothing else than an imaginary point in space, or the potency of a real centre of power. This clear and definite conception of the first matter is calculated to shed some additional light on many questions connected with the peripatetic philosophy, and, above all, on the very definition of matter. The old metaphysicians, when defining the first matter to be “a pure potency,” had no notion of the existence of simple elements, and knew very little about the law of material actions; and for this reason they could say nothing about the special character of such a pure potency. For the same reason they were unable also to point out the special nature of the first act of matter; they simply recognized that the conspiration of such a potency with such an act ought to give rise to a “movable being.” But potency and act are to be found not only in material, but also in spiritual, substances; and as these substances are of a quite different nature, it is evident that their respective potencies and their respective acts must be of a quite different nature. Now, the special character of the potency of material substance consists in its being a _local_ term, whilst the special character of the potency of spiritual substance consists in its being an _intellectual_ term. And therefore, to distinguish the former from the latter, we should say that the matter is “a potential term _in space_” and the first matter “a potency of being in space.” The additional words “_in space_” point out the characteristic attribute of the material potency as distinguished from all other potencies.