3. Descartes never reached the third part, the philosophy of Mind, for, while he made a special study of physics, in the region of ethics he published one tract only, _De passionibus_. In this reference Descartes treats of thought and human freedom. He proves freedom from the fact of the soul thinking that the will is unrestrained, and of that constituting the perfection of mankind. And this is quite true. In respect to the freedom of the will he comes across the difficulty of how to reconcile it with the divine prescience. As free, man might do what is not ordained of God beforehand—this would conflict with the omnipotence and omniscience of God; and if everything is ordained of God, human freedom would thereby be done away with. Yet he does not solve the contradiction contained in these two different aspects without falling into difficulty. But conformably to the method which he adopts, and which we pointed out above (pp. 238, 239), he says: “The human mind is finite, God’s power and predetermination are infinite; we are thus not capable of judging of the relationship in which the freedom of the human soul stands to the omnipotence and omniscience of God—but in self-consciousness we have the certainty of it given us as a fact. And we must hold only to what is certain.”[190] When he proceeds further much appears to him still incapable of explanation; but we see obstinacy and caprice likewise exhibited in his stopping short at the assertion as to the best of his knowledge. The method of knowledge as set forth by Descartes, takes the form of a reasoning of the understanding, and is thus without special interest. These, then, are the principal points in the Cartesian system. Some particular assertions made by Descartes, which have been specially instrumental in giving him fame, have still to be mentioned—particular forms which have been formerly considered in metaphysics, and likewise by Wolff. For example, in the first place we gather that Descartes regarded animals and other organisms as machines moved by another, and not possessing the principle of the spontaneity of thought within them[191]—a mechanical physiology, a cut and dry thought pertaining to the understanding, which is of no further importance. In the sharp opposition between thought and extension, the former is not considered as sensation, so that the latter can isolate itself. The organic must as body reduce itself to extension; any further development of this last thus only proves its dependence on the first determinations.