VIII.

The social studies through which we have accompanied Plato seem to have reacted on his more abstract speculations, and to have largely modified the extreme opposition in which these had formerly stood to current notions, whether of a popular or a philosophical character. The change first becomes perceptible in his theory of Ideas. This is a subject on which, for the sake of greater clearness, we have hitherto refrained from entering; and that we should have succeeded in avoiding it so long would seem to prove that the doctrine in question forms a much less important part of his philosophy than is commonly imagined. Perhaps, as some think, it was not an original invention of his own, but was borrowed from the Megarian school; and the mythical connexion in which it frequently figures makes us doubtful how far he ever thoroughly accepted it. The theory is, that to every abstract name or conception of the mind there corresponds an objective entity possessing a separate existence quite distinct from that of the scattered particulars by which it is exemplified to our senses or to our imagination. Just as the Heracleitean flux represented the confusion of which Socrates convicted his interlocutors, so also did these Ideas represent the definitions by which he sought to bring method and certainty into their opinions. It may be that, as Grote suggests, Plato adopted this hypothesis in order to escape from the difficulty of defining common notions in a satisfactory manner. It is certain that his earliest Dialogues seem to place true definitions beyond the reach of human knowledge. And at the beginning of Plato’s constructive period we find the recognition of abstract conceptions, whether mathematical or moral, traced to the remembrance of an ante-natal state, where the soul held direct converse with the transcendent realities to which those conceptions correspond. Justice, temperance, beauty, and goodness, are especially mentioned as examples of Ideas revealed in this manner. Subsequent investigations must, however, have led Plato to believe that the highest truths are to be found by analysing not the loose contents but the fixed forms of consciousness; and that, if each virtue expressed a particular relation between the various parts of the soul, no external experience was needed to make her acquainted with its meaning; still less could conceptions arising out of her connexion with the material world be explained by reference to a sphere of purely spiritual existence. At the same time, innate ideas would no longer be required to prove her incorporeality, when the authority of reason over sense furnished so much more satisfactory a ground for believing the two to be of different origin. To all who have studied the evolution of modern thought, the substitution of Kantian forms for Cartesian ideas will at once elucidate and confirm our hypothesis of a similar reformation in Plato’s metaphysics.

Again, the new position occupied by Mind as an intermediary between the world of reality and the world of appearance, tended more and more to obliterate or confuse the demarcations by which they had hitherto been separated. The most general headings under which it was usual to contrast them were, the One and the Many, Being and Nothing, the Same and the Different, Rest and Motion. Parmenides employed the one set of terms to describe his Absolute, and the other to describe the objects of vulgar belief. They also served respectively to designate the wise and the ignorant, the dialectician and the sophist, the knowledge of gods and the opinions of men; besides offering points of contact with the antithetical couples of Pythagoreanism. But Plato gradually found that the nature of Mind could not be understood without taking both points of view into account. Unity and plurality, sameness and difference, equally entered into its composition; although undoubtedly belonging to the sphere of reality, it was self-moved and the cause of all motion in other things. The dialectic or classificatory method, with its progressive series of differentiations and assimilations, also involved a continual use of categories which were held to be mutually exclusive. And on proceeding to an examination of the summa genera, the highest and most abstract ideas which it had been sought to distinguish by their absolute purity and simplicity from the shifting chaos of sensible phenomena, Plato discovered that even these were reduced to a maze of confusion and contradiction by a sincere application of the cross-examining elenchus. For example, to predicate being of the One was to mix it up with a heterogeneous idea and let in the very plurality which it denied. To distinguish them was to predicate difference of both, and thus open the door to fresh embarrassments.

Finally, while the attempt to attain extreme accuracy of definition was leading to the destruction of all thought and all reality within the Socratic school, the dialectic method had been taken up and parodied in a very coarse style by a class of persons called Eristics. These men had, to some extent, usurped the place of the elder Sophists as paid instructors of youth; but their only accomplishment was to upset every possible assertion by a series of verbal juggles. One of their favourite paradoxes was to deny the reality of falsehood on the Parmenidean principle that ‘nothing cannot exist.’ Plato satirises their method in the _Euthydêmus_, and makes a much more serious attempt to meet it in the _Sophist_; two Dialogues which seem to have been composed not far from one another.[156] The _Sophist_ effects a considerable simplification in the ideal theory by resolving negation into difference, and altogether omitting the notions of unity and plurality,—perhaps as a result of the investigations contained in the _Parmenides_, another dialogue belonging to the same group, where the couple referred to are analysed with great minuteness, and are shown to be infected with numerous self-contradictions. The remaining five ideas of Existence, Sameness, Difference, Rest, and Motion, are allowed to stand; but the fact of their inseparable connexion is brought out with great force and clearness. The enquiry is one of considerable interest, including, as it does, the earliest known analysis of predication, and forming an indispensable link in the transition from Platonic to Aristotelian logic—that is to say, from the theory of definition and classification to the theory of syllogism.

Once the Ideas had been brought into mutual relation and shown to be compounded with one another, the task of connecting them with the external world became considerably easier; and the same intermediary which before had linked them to it as a participant in the nature of both, was now raised to a higher position and became the efficient cause of their intimate union. Such is the standpoint of the _Philêbus_, where all existence is divided into four classes, the limit, the unlimited, the union of both, and the cause of their union. Mind belongs to the last and matter to the second class. There can hardly be a doubt that the first class is either identical with the Ideas or fills the place once occupied by them. The third class is the world of experience, the Cosmos of early Greek thought, which Plato had now come to look on as a worthy object of study. In the _Timaeus_, also a very late Dialogue, he goes further, and gives us a complete cosmogony, the general conception of which is clear enough, although the details are avowedly conjectural and figurative; nor do they seem to have exercised any influence or subsequent speculation until the time of Descartes. We are told that the world was created by God, who is absolutely good, and, being without jealousy, wished that all things should be like himself. He makes it to consist of a soul and a body, the former constructed in imitation of the eternal archetypal ideas which now seem to be reduced to three—Existence, Sameness, and Difference.[157] The soul of the world is formed by mixing these three elements together, and the body is an image of the soul. Sameness is represented by the starry sphere rotating on its own axis; Difference by the inclination of the ecliptic to the equator; Existence, perhaps, by the everlasting duration of the heavens. The same analogy extends to the human figure, of which the head is the most essential part, all the rest of the body being merely designed for its support. Plato seems to regard the material world as a sort of machinery designed to meet the necessities of sight and touch, by which the human soul arrives at a knowledge of the eternal order without;—a direct reversal of his earlier theories, according to which matter and sense were mere encumbrances impeding the soul in her efforts after truth.

What remains of the visible world after deducting its ideal elements is pure space. This, which to some seems the clearest of all conceptions, was to Plato one of the obscurest. He can only describe it as the formless substance out of which the four elements, fire, air, water, and earth, are differentiated. It closes the scale of existence and even lies half outside it, just as the Idea of Good in the _Republic_ transcends the same scale at the other end. We may conjecture that the two principles are opposed as absolute self-identity and absolute self-separation; the whole intermediate series of forms serving to bridge over the interval between them. It will then be easy to understand how, as Aristotle tells us, Plato finally came to adopt the Pythagorean nomenclature and designated his two generating principles as the monad and the indefinite dyad. Number was formed by their combination, and all other things were made out of number. Aristotle complains that the Platonists had turned philosophy into mathematics; and perhaps in the interests of science it was fortunate that the transformation occurred. To suppose that matter could be built up out of geometrical triangles, as Plato teaches in the _Timaeus_, was, no doubt, a highly reprehensible confusion; but that the systematic study of science should be based on mathematics was an equally new and important aperçu. The impulse given to knowledge followed unforeseen directions; and at a later period Plato’s true spirit was better represented by Archimedes and Hipparchus than by Arcesilaus and Carneades.

It is remarkable that the spontaneous development of Greek thought should have led to a form of Theism not unlike that which some persons still imagine was supernaturally revealed to the Hebrew race; for the absence of any connexion between the two is now almost universally admitted. Modern science has taken up the attitude of Laplace towards the hypothesis in question; and those critics who, like Lange, are most imbued with the scientific spirit, feel inclined to regard its adoption by Plato as a retrograde movement. We may to a certain extent agree with them, without admitting that philosophy, as a whole, was injured by departing from the principles of Democritus. An intellectual like an animal organism may sometimes have to choose between retrograde metamorphosis and total extinction. The course of events drove speculation to Athens, where it could only exist on the condition of assuming a theological form. Moreover, action and reaction were equal and contrary. Mythology gained as much as philosophy lost. It was purified from immoral ingredients, and raised to the highest level which supernaturalism is capable of attaining. If the _Republic_ was the forerunner of the Catholic Church, the _Timaeus_ was the forerunner of the Catholic faith.