A Beginner's History of Philosophy, Vol. 1: Ancient and Mediæval Philosophy

by Herbert Ernest Cushman

The Divisions of Plato’s Philosophy. Plato himself had no clear conception of an exact division of science, and did not confine himself in a single dialogue to a single science. Aristotle, however, distinguished in the philosophy of his master dialectic, ethics, and physics, and these divisions of Plato’s teaching have been traditionally adopted. The dialectic, as commonly used in his time, meant “the dialogue or conversation employed as a means of scientific investigation.” It was transformed by Plato to mean not logical but metaphysical discussion. Plato was concerned with the laws of Being rather than the laws of logic, and, as Being to him consisted of Ideas, his dialectic interest was to reduce experience by division and induction to some unity. Plato’s dialectic was not logical but methodological,—logical operations taken as a whole,—by means of which the Ideas and their relations to one another were to be found. The physics of Plato is of little value. It was an afterthought to satisfy the demands of his school. The world of nature phenomena could never be for Plato the object of true knowledge. Unfortunately, the teleological physics of Plato was regarded by the Hellenistic time and the Middle Ages as Plato’s most important achievement. Plato wrote entirely in the spirit of the Enlightenment, and his works show a great interest in man as a moral being, but little interest in physical nature.

Summary of Plato’s Doctrine. The interpretation of Plato as set forth in what follows may be thus summarized: Plato began with the conceptual form of idealism, suggested by the logical method of Socrates, with the purpose of solving logical and ethical problems. He advanced to a teleological idealism, conditioned by the doctrines of Anaxagoras and the Pythagoreans, with the purpose of applying his doctrine to physical problems.

The Formation of Plato’s Metaphysics. In his earliest period Plato made these very clear statements: (1) virtue is knowledge; (2) by knowledge is not meant sense-perceptions. In his final statement of his philosophy, as he bequeathed it to posterity, he only gave a new evaluation of these two early principles, although he expressed them in a highly complex form. “Virtue is knowledge” is the basis of agreement between Socrates and the Sophists; and “by knowledge is not meant sense-perceptions” is the basis of their opposition. During Plato’s early period he was acting as a faithful transcriber of Socrates in the presentation of this first principle: virtue is knowledge, is teachable, is one. DuringPlato’s second period he was called on to defend the second statement against the Sophists. Plato’s formation of his own theory begins at this point,—at the point where his defense of his master was keenest. From this time, for a full half-century, Plato developed the Socratic principles in a theory that went far beyond Socrates, but that was never untrue to him.

The simplest way of stating Plato’s formation of his own doctrine is this: he accepted the Protagorean doctrine of a perceptual world of relative knowledge; he placed it beside the Socratic theory of conceptual reality; and as a result he conceived the world to be twofold. Both Being and Becoming share in reality. There are, on the one side, the immutable concepts that compose true reality; there are, on the other side, the changing perceptions that come and go. The world of true reality is, but never becomes; the world of relative reality becomes, but never is. These two worlds are by nature separate; one is the object of the reason, the other is the object of the senses; one is incorporeal, the other is corporeal. The first world is the immutable One of the Eleatics presented by Plato as a plural number of Socratic concepts; the other world is the Heracleitan flux presented as perceivable things. There is true knowledge, but Protagoras is right in saying that it cannot be found in the perception of the material world. It is knowledge of an incorporeal world, and that is precisely the world of Socratic concepts which now in Plato’s hands become Ideas.

It would, however, be a mistake to suppose that Plato’s conception of the world was an artificial eclecticism, obtained by putting two worlds side by side. To be sure, he never was able to bring them into an organicunity, and the dualism between them is often very marked. But they do not lie like two drawers in a desk, each having no vital influence on the character of the other. In the juxtaposition of the two worlds each gets a new meaning, and the value of each becomes greater.

In the first place, perception[30] gets a new value. The logic of the Sophistic doctrine of perception was that perceptions are the only form of knowledge, and even perceptions have no share of truthfulness. Protagoras himself did not go so far as this absolute skepticism, but this is the logic of his position. Perceptions can have no value, because each is a standard to itself. Plato incorporates the perception theory into his own, and immediately gives it a new value. Perceptions do not, to be sure, yield true knowledge, but they have a relative value. They have a value for the practical world, although the highest they can give is Right Opinion. When we remember that the world of that day was weary of its own speculations leading to nihilism, it is remarkable that Plato did not turn away entirely from the doctrine of the Sophists. On the contrary, he took up the Sophistic doctrine into his own and gave to it a value which it had not possessed by itself.

In the second place, conception gets a new value. What was conception to Socrates? It was the common content of opinions and perceptions; it was the universal that was developed inductively out of many particulars. Socrates brought many particulars together in order to reveal their common qualities. The abode of conceptions was to Socrates the half-formed individual opinions and experiences in which conception lay, as inan envelope; and the conversation was needed to bring it forth. The concept to Socrates was the logical “nature” of perceptions. But now since Plato admitted the relative reality of all perceptions, he was obliged to look elsewhere to account for conceptions. If the conceptions are true reality, they cannot be the common quality in opinions, nor the logical “nature” of changing perceptions. The true conception cannot be contained in the perception. Accordingly the conception must exist in an incorporeal world and possess an independent reality. The concepts are hypostasized by Plato. They become Ideas. Thus the Socratic concept became the Platonic Idea, and for the first time in European thought, reality is conceived as immaterial. The conceptual world grows under Plato’s hands to be “other than” the perceptual world, and this was his first step beyond Socrates. The conceptual world is the perfect reality that cannot be contained in any material thing nor in the sum of all material things. The immaterial Ideas are the object of thought, as nature phenomena are the objects of perception. Ideas are not the abstractions of perceptions, for the process of thought is not an analysis nor an abstraction, but an intuition of reality presented in single instances. Ideas are the reality of which perceptions are the copies or shadows. Perceptions do not contain the truth. They are only the suggestions or promptings by which the soul bethinks itself of the Ideas. Material things merely hint to the soul of the existence of the Ideas.

It is important in this connection to point out that Plato’s conception of immateriality is not to be taken as what we mean in modern times by the spiritual or psychical; for, according to Plato, our psychical functionsbelong to the world of Becoming, just as the functions of our body and other perceptual things belong to it. Besides, even the Ideas of sense qualities have reality. Plato does not identify the human mind with the incorporeal world of Ideas, nor does he make the modern dualistic division of the world into mind and matter. The immaterial world is “other than” the world of perception, and bears the relation to the material world of the unchanging to the changing, of the simple to the manifold, of Being to Becoming.

The Development of Plato’s Metaphysics—The Development of Plato’s Ideas in the Two Drafts. The twofold world with its new evaluation of the Socratic conception and of the Protagorean perception was, after all, only Plato’s point of departure for his constructive work. It was his first and undeveloped apprehension of a theory of Ideas. It appeared first in the Meno in his doctrine of recollection and immortality, which was written in his second period just after his series of splendid polemics against the Sophists. From this time for a full half-century Plato developed the conception of a twofold world into a Theory of Ideas. In the course of time he found himself confronted with three problems: (1) How many Ideas are there? (2) What is the relation between Ideas and physical things? (3) What is the relation of the Ideas to one another? Plato’s answers to these three questions compose what is known as his Theory of Ideas. However, he answers these three questions differently when he first considered them than later, when his grasp upon the significance of his problem became more mature. Plato’s Theory of Ideas, therefore, may be said to have had a development in two stages. These two stages are calledhis “two drafts” (Windelband) of the Ideas. We shall now present, first in summary form and then in more detail, his answers to these three questions in the two drafts, and thereby show how his theory developed to its final formulation.

Brief Comparison of the Two Drafts of the Ideas.