But a philosophical system has been projected. The real is that perfect significance or meaning which thought and every interest suggests, and toward which there is in experience an appreciable movement. It is this significance which makes things what they really are, and which constitutes our understanding of them. In itself it transcends the steps which lead to it; "for God," says Plato, "mingles not with men." But it is nevertheless the meaning of human life. And this we can readily conceive. The last word may transform the sentence from nonsense into sense, and it would be true to say that its sense mingles not with nonsense. Similarly the last touch of the brush may transform an inchoate mass of color into a picture, disarray into an object of beauty; and its beauty mingles not with ugliness. So life, when it finally realizes itself, obtains a new and incommensurable quality of perfection in which humanity is transformed into deity. There is frankly no provision for imperfection in such a world. In his later writings Plato sounds his characteristic note less frequently, and permits the ideal to create a cosmos through the admixture of matter. But in his moment of inspiration, the Platonist will have no sense for the imperfect. It is the darkness behind his back, or the twilight through which he passes on his way to the light. He will use even the beauties of earth only "as steps along which he mounts upward for the sake of that other beauty." [Sidenote: Aristotle's Hierarchy of Substances in Relation to Platonism.] § 162. We have met, then, with two distinct philosophical doctrines which arise from the conception of the _absolute_, or the philosopher's peculiar object: the doctrine of the _absolute being_ or _substance_, and that of the _absolute ideal_ or _good_. Both doctrines are realistic in that they assume reality to be demonstrated or revealed, rather than created, by knowledge. Both are rationalistic in that they develop a system of philosophy from the problem of philosophy, or deduce a definition of reality from the conception, of reality. There remains a third doctrine of the same type--the philosophy of Aristotle, the most elaborately constructed system of Greek antiquity, and the most potent influence exerted upon the Scholastic Philosophy of the long mediæval period. This philosophy was rehabilitated in the eighteenth century by Leibniz, the brilliant librarian of the court of Hanover. The extraordinary comprehensiveness of Aristotle's philosophy makes it quite impossible to render here even a general account of it. There is scarcely any human discipline that does not to some extent draw upon it. We are concerned only with the central principles of the metaphysics.