This theory, which conducts from absolute truth to absolute being, is not new in the history of philosophy: it goes back to Plato.
Plato,[46] in searching for the principles of knowledge clearly saw, with Socrates his master, that the least definition, without which there can be no precise knowledge, supposes something universal and one, which does not come within the reach of the senses, which reason alone can discover; this something universal and one he called Idea.
Ideas, which possess universality and unity, do not come from material, changing, and mobile things, to which they are applied, and which render them intelligible. On the other hand, it is not the human mind that constitutes ideas; for man is not the measure of truth.
Plato calls Ideas veritable beings, τὰ οντως ὄντα, since they alone communicate to sensible things and to human cognitions their truth and their unity. But does it follow that Plato gives to Ideas a substantial existence, that he makes of them beings properly so called? It is important that no cloud should be left on this fundamental point of the Platonic theory.
At first, if any one should pretend that in Plato Ideas are beings subsisting by themselves, without interconnection and without relation to a common centre, numerous passages of the Timaeus might be objected to him,[47] in which Plato speaks of Ideas as forming in their whole an ideal unity, which is the reason of the unity of the visible world.[48]
Will it be said that this ideal world forms a distinct unity, a unity separate from God? But, in order to sustain this assertion, it is necessary to forget so many passages of the Republic, in which the relations of truth and science with the Good, that is to say, with God, are marked in brilliant characters.
Let not that magnificent comparison be forgotten, in which, after having said that the sun produces in the physical world light and life, Socrates adds: "So thou art able to say, intelligible beings not only hold from the Good that which renders them intelligible, but also their being and their essence."[49] So, intelligible beings, that is to say, Ideas, are not beings that exist by themselves.
Men go on repeating with assurance that the Good, in Plato, is only the idea of the good, and that an idea is not God. I reply, that the Good is in fact an idea, according to Plato, but that the idea here is not a pure conception of the mind, an object of thought, as the peripatetic school understood it; I add, that the Idea of the Good is in Plato the first of Ideas, and that, for this reason, while remaining for us an object of thought, it is confounded as to existence with God. If the Idea of the Good is not God himself, how will the following passage, also taken from the Republic, be explained? "At the extreme limits of the intellectual world is the Idea of the Good, which is perceived with difficulty, but, in fine, cannot be perceived without concluding that it is the source of all that is beautiful and good; that in the visible world it produces light, and the star whence the light directly comes, that in the invisible world it directly produces truth and intelligence."[50] Who can produce, on the one hand, the sun and light, on the other, truth and intelligence, except a real being?
But all doubt disappears before the following passages from the Phædrus, neglected, as it would seem designedly, by the detractors of Plato: "In this transition, (the soul) contemplates justice, contemplates wisdom, contemplates science, not that wherein enters change, nor that which shows itself different in the different objects which we are pleased to call beings, but science as it exists in that which is called being, par excellence...."[51]—"It belongs to the soul to conceive the universal, that is to say, that which, in the diversity of sensations, can be comprehended under a rational unity. This is the remembrance of what the soul has seen during its journey in the train of Deity, when, disdaining what we improperly call beings, it looked upwards to the only true being. So it is just that the thought of the philosopher should alone have wings; for its remembrance is always as much as possible with the things which make God a true God, inasmuch as he is with them."[52]
So the objects of the philosopher's contemplation, that is to say, Ideas, are in God, and it is by these, by his essential union with these, that God is the true God, the God who, as Plato admirably says in the Sophist, participates in august and holy intelligence.[53]