THREE:Turning back once more from the melancholy decline of a great genius to the splendour of its meridian prime, we will endeavour briefly to recapitulate the achievements which entitle Plato to rank among the five or six greatest Greeks, and among the four or five greatest thinkers of all time. He extended the philosophy of mind until it embraced not only ethics and dialectics but also the study of politics, of religion, of social science, of fine art, of economy, of language, and of education. In other words, he showed how ideas could be applied to life on the most comprehensive scale. Further, he saw that the study of Mind, to be complete, necessitates a knowledge of physical phenomena and of the realities which underlie them; accordingly, he made a return on the objective speculations which had been temporarily abandoned, thus mediating between Socrates and early Greek thought; while on the other hand by his theory of classification he mediated between Socrates and Aristotle. He based physical science273 on mathematics, thus establishing a method of research and of education which has continued in operation ever since. He sketched the outlines of a new religion in which morality was to be substituted for ritualism, and intelligent imitation of God for blind obedience to his will; a religion of monotheism, of humanity, of purity, and of immortal life. And he embodied all these lessons in a series of compositions distinguished by such beauty of form that their literary excellence alone would entitle them to rank among the greatest masterpieces that the world has ever seen. He took the recently-created instrument of prose style and at once raised it to the highest pitch of excellence that it has ever attained. Finding the new art already distorted by false taste and overlaid with meretricious ornament, he cleansed and regenerated it in that primal fount of intellectual life, that richest, deepest, purest source of joy, the conversation of enquiring spirits with one another, when they have awakened to the desire for truth and have not learned to despair of its attainment. Thus it was that the philosophers mastery of expression gave added emphasis to his protest against those who made style a substitute for knowledge, or, by a worse corruption, perverted it into an instrument of profitable wrong. They moved along the surface in a confused world of words, of sensations, and of animal desires; he penetrated through all those dumb images and blind instincts, to the central verity and supreme end which alone can inform them with meaning, consistency, permanence, and value. To conclude: Plato belonged to that nobly practical school of idealists who master all the details of reality before attempting its reformation, and accomplish their great designs by enlisting and reorganising whatever spontaneous forces are already working in the same direction; but the fertility of whose own suggestions it needs more than one millennium to exhaust. There is nothing in heaven or earth that was not dreamt of in his philosophy:274 some of his dreams have already come true; others still await their fulfilment; and even those which are irreconcilable with the demands of experience will continue to be studied with the interest attaching to every generous and daring adventure, in the spiritual no less than in the secular order of existence.To understand Descartes aright, we must provisionally disregard the account given in his work on Method of the process by which he arrived at a new theory of the world; for, in truth, there was nothing new about it except the pro388portion in which fragments taken from older systems were selected and recombined. As we have already noticed, there is no such thing as spinning philosophies out of ones own head; and, in the case of Descartes, even the belief that he was so doing came to him from Plato; for, along with Aristotles dogmatic errors, his sound teaching with regard to the derivation of knowledge had fallen into oblivion. The initial doubt of the Discourse on Method and the Meditations is also Platonic; only it is manifested under an individual and subjective, instead of a universal and objective form. But to find the real starting-point of Descartes enquiries we must look for it in his mathematical studies. A geometrician naturally conceives the visible world under the aspect of figured extension; and if he thinks the figures away, nothing will remain but extension as the ultimate material out of which all determinate bodies are shaped. Such was the result reached by Plato in his Timaeus. He identified matter with space, viewing this as the receptacle for his eternal and self-existent Ideas, or rather the plastic medium on which their images are impressed. The simplest spatial elements are triangles; accordingly it is with these that he constructs his solid bodies. The theory of triangular elements was probably suggested by Atomism; it is, in fact, a compromise between the purely mathematical and the materialistic methods. Like all Platos fancies, this theory of matter was attacked with such convincing arguments by Aristotle that, so long as his physics remained in the ascendent, it did not find a single supporter; although, as we saw in the last chapter, Plotinus very nearly worked his way back to it from the Peripatetic definition. Even now, at the moment of Aristotles fall, it might have failed to attract attention, had not the conditions under which it first arose been almost exactly repeated. Geometrical demonstration had again become the type of all reasoning; there was again a sceptical spirit abroad, forcing men to fall back on the most elementary and universal con389ceptions; an atomistic materialism again threatened to claim at least the whole field of physical enquiry for its own. That Descartes followed the Timaeus in identifying matter with extension cannot be doubted; especially when we see that he adopts Platos analysis of body into elementary triangles; but the theory agreed so well with his intellectual predispositions that he may easily have imagined it to be a necessary deduction from his own priori ideas. Moreover, after the first two steps, he parts company with Plato, and gives himself up, so far as his rejection of a vacuum will permit, to the mechanical physics of Democritus. Much praise has recently been bestowed on his attempt to interpret all physical phenomena in terms of matter and motion, and to deduce them from the unaided operation of natural causes; but this is no more than had been done by the early Greek thinkers, from whom, we may observe, his hypothesis of an initial vortex was also derived. His cosmogony is better than theirs, only in so far as it is adapted to scientific discoveries in astronomy and physiology not made by Descartes himself; for where his conjectures go beyond these they are entirely at fault.
