In the Republic, we have a repetition and copious illustration of this antithesis between the world of Universals or Cogitables, which are the only unchangeable realities and the only objects of knowledge, — and the world of Sensible Particulars, which are transitory and confused shadows of these Universals, and are objects of opinion only. Full and real Ens is knowable, Non-Ens is altogether unknowable; what is midway between the two is matter of opinion, and in such midway are the Particulars of sense.[7] Respecting these last, no truth is attainable: whenever you affirm a proposition respecting any of them, you may with equal truth affirm the contrary at the same time. Nowhere is the contrast between the Universals or real Ideas (among which the Idea of Good is the highest, predominant over all the rest), and the unreal Particulars, or Percepta, of Sense, more forcibly insisted upon than in the Republic. Even the celestial bodies and their movements, being among these Percepta of sense, are ranked among phantoms interesting but useless to observe; they are the best of all Percepta, but they fall very short of the perfection that the mental eye contemplates in the Ideal — in the true Figures and Numbers, in the real Velocity and the real Slowness. In the simile commencing the seventh book of the Republic, Plato compares mankind to prisoners in a cave, chained in one particular attitude, so as to behold only an ever-varying multiplicity of shadows, projected, through the opening of the cave upon the wall before them, by certain unseen realities behind. The philosopher is one among a few, who by training or inspiration, have been enabled to face about from this original attitude, and to contemplate with his mind the real unchangeable Universals, instead of having his eye fixed upon their particular manifestations, at once shadowy and transient. By such mental revolution he comes round from the Perceivable to the Cogitable, from Opinion to Knowledge.
[7] Plato, Republic. v. pp. 477, 478.
The distinction between these two is farther argued in the elaborate dialogue called Theætetus, where Sokrates, trying to explain what Knowledge or Cognition is, refutes three proposed explanations and shows, to his own satisfaction, that it is not sensible perception, that it is not true opinion, that it is not true opinion coupled with rational explanation. But he confesses himself unable to show what Knowledge or Cognition is, though he continues to announce it as correlating with Realities Cogitable and Universal only.[8]
[8] Plato, Theætêt. pp. 173, 176, 186. Grote’s Plato, II. [xxvi.] pp. 320-395.
In the passages above noticed, and in many others besides, we find Plato drawing a capital distinction between Universals eternal and unchangeable (each of them a Unit as well as a Universal),[9] which he affirms to be the only real Entia, — and Particulars transient and variable, which are not Entia at all, but are always coming or going; the Universals being objects of cogitation and of a psychological fact called Cognition, which he declares to be infallible; and the Particulars being objects of Sense, and of another psychological fact radically different, called Opinion, which he pronounces to be fallible and misleading. Plato holds, moreover, that the Particulars, though generically distinct and separate from the Universals, have nevertheless a certain communion or participation with them, by virtue of which they become half existent and half cognizable, but never attain to full reality or cognizability.
[9] Plato, Philêbus, p. 15, A. B.; Republic, x. p. 596, A. The phrase of Milton, “unus et universus,� expresses this idea; also the lines:—
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“Sed quamlibet natura sit communior, Tamen seorsus extat ad modum unius,� &c. |
This is the first statement of the theory of complete and unqualified Realism, which came to be known in the Middle Ages under the phrase Universalia ante rem or extra rem, and to be distinguished from the two counter-theories Universalia in re (Aristotelian), and Universalia post rem (Nominalism). Indeed, the Platonic theory goes even farther than the phrase Universalia ante rem, which recognizes the particular as a reality, though posterior and derivative; for Plato attenuates it into phantom and shadow. The problem was now clearly set out in philosophy — What are the objects correlating with Universal terms, and with Particular terms? What is the relation between the two? Plato first gave to the world the solution called Realism, which lasted so long after his time. We shall presently find Aristotle taking issue with him on both the affirmations included in his theory.
But though Plato first introduced this theory into philosophy, he was neither blind to the objections against it, nor disposed to conceal them. His mind was at once poetically constructive and dialectically destructive; to both these impulses the theory furnished ample scope, while the form of his compositions (separate dialogues, with no mention of his own name) rendered it easy to give expression either to one or to the other. Before Aristotle arose to take issue with him, we shall find him taking issue with himself, especially in the dialogues called Sophistes and Parmenides, not to mention the Philêbus, wherein he breaks down the unity even of his sovereign Idea, which in the Republic governs the Cogitable World, — the Idea of Good.[10]
[10] Plato, Philêbus, pp. 65, 66. See Grote’s Plato, II. xxx. pp. [584, 585].