Aristotle's distinction of form and matter in nature, of pure activity and pure passivity, had still sufficient influence to render even in Bruno's time a purely mechanical treatment of nature an impossibility. The opposing school, the Neo-Platonism which attracted so many minds of that period, because of its supposed inconsistency with Aristotle's system, was itself an offshoot, to some extent, of that system, and was still less scientific in its tendency. Mysticism, of which it was partly a cause and partly an effect, lent its weight also against any mechanical interpretation of nature. Thus even while apparently governed by scientific aspiration, Bruno gives a teleological scheme of the universe which renders any scientific explanation of it impossible. Not only, as we have seen, is the ether identified with the first substance, spirit, or soul of the universe, but also the greater and lesser organic bodies are governed each by its individual soul, which is somehow distinguished from the universal spirit, and within each of these is an infinite number of smaller living bodies. In other words, the atoms themselves are animated _virtually_, if not _actually_. This animistic interpretation is in direct conflict with the mechanical interpretation which science has followed, and which it must continue to follow if it is to produce any result. Thus, motion and the changes of composition that derive from motion are explained not by the mechanical impact of atoms and bodies upon one another, but by the action of the intrinsic soul in each being, which causes the motion of the body, in accordance with its need and desire of self-preservation. All motion, even the slightest, is thus explained by a final cause. In the whole universe also, the constantly occurring changes and transformations are due to a similar final cause--the need for each thing to become _explicitly_ that which it already is _implicitly_, _i.e._ the whole of reality. It required once more a critical separation of the spheres of validity of the respective conceptions of nature and spirit, such as Kant attempted, before full scope could be given to mechanical interpretation on the one side, and teleology restricted to the domain of spirit only on the other. CHAPTER VI THE PRACTICAL PHILOSOPHY OF BRUNO