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

by Herbert Ernest Cushman

2. The Relation of Ideas and the World of Nature in the Two Drafts compared. Plato did not construct his world of Ideas in order to explain the world of physical nature. His original purpose was to find an object for knowledge; and his Ideas were born out of his striving to give a reality to the conceptions of Socrates. In his evaluation of the doctrine of his masterhe had drawn a distinction between the two worlds, but he had not thought of explaining one by the other. They were related and distinguished, but one threw no light upon the other. In Plato’s first draft of the Ideas he speaks of this relation as imitation. The phenomena are an imitation of reality. The Ideas are the originals and physical objects are copies. To state the relation in modern terms, the laws of the growth of a tree are permanent, while the tree changes. The lower world of Becoming has a similarity to the higher world of Being. As the Pythagoreans had conceived things as imitations of numbers, Plato, strongly influenced by the Pythagoreans, thought that concrete things correspond to their class concepts only in a degree. On the one hand, the individual thing partakes of the universal of the Idea, and this is called “participation” in the Idea. On the other hand, the word “presence” describes the way the Idea exists in the thing, which means that the Idea is present in the thing so long as the thing possesses the quality of the Idea. The Ideas are present and then withdraw, and thus the perception changes.

In the second drafting of the Ideas, Plato has become conscious of the need of explaining physical nature by the Ideas. He did not at first think of explaining the nature of the physical world by his metaphysical reality. It was an afterthought, and arose out of the compulsion of having a systematic theory. His conception of the world of Ideas as the world of true Being ultimately demanded that the world of physical nature should be not merely “other than” but dependent upon the Ideas. The Ideas are unchanging; the phenomena are changing. If the Ideas are the realityof the changing world, in what other sense can they be its reality than as its cause? The Meno, Theætetus, Symposium, and Phædrus do not discuss this problem. The Sophist proposes it, and in the Phædo the thought is first expressed that the Ideas are the causes of physical phenomena appearing as they do appear. But how can the Ideas be causes, when the very conception of them as pure and immaterial realities denies to them all qualities of motion and change? The Platonic theory reached its zenith in its solution of this problem. The Ideas must be conceived as the causes of nature phenomena, and still as not moving nor suffering change. They are teleological causes. They are the realized ends of the phenomenal world. The world of Ideas is the actual goal of perfection for physical nature. The world of Ideas is not only the truth of all knowledge; it is also the perfect teleological cause of all actual change. This thought is developed in the Philebus and the Republic, where the Ideas as a whole, and in particular the Idea of the Good,—to which all the other Ideas are means,—stand as the final cause of all occurrence. The physical phenomena stand therefore in a teleological relation to the Idea of the Good. From the Good all things get their meaning. It permeates and explains all.

3. The Relation among the Ideas in the Two Drafts compared. It was natural that the conception of a pluralism of Ideas should lead Plato to a consideration of the law of their relationship. A systematic theory of a multiplicity of reals involves their orderly relationship. They cannot exist independently in the same world. What is the relationship among the Ideas? In the earlier drafting of his theory Plato was principallyattentive to the relations of coördination and subordination among the Ideas; in the possibility of the division of class concepts into genera and species. The relationship that he sought was logical relationship, the relationship that the scientist seeks to find in the classification of plants or rocks. Just what result Plato tried to reach by such a logical classification of his realities, it is difficult to say. He was not successful. His attempt to erect a logically arranged pyramid of conceptions with the most abstract at the apex was not carried out.

In his second drafting of the Ideas, Plato felt the inadequacy of a mere logical relationship among them, and conceived them to be teleologically related. His reduction of the number of Ideas had naturally brought about a new conception of their relationship. There must be some principle for their elimination, for the rejecting of some and the keeping of others. That principle was the principle of their ethical worth. That is to say, the Idea of the Good, which had been the standard for eliminating some concepts from the list of Ideas and for retaining others, now became for him the principle of the relationship of the Ideas among themselves. Plato turned from the logical to the teleological relation among Ideas. The Idea of the Good embraces and realizes all the others. It is therefore the absolute end of all the other Ideas, and they bear the relation to it, not of particulars to a general term, but of means to an end. The principle in their selection becomes the principle of their arrangement.

Plato’s Conception of God. The above sketch of the formation and development of Plato’s theory of Ideas shows how difficult it would be to frame a short definitionof them that would at the same time be adequate. As he finally defined them, they are immaterial archetypes or ideals, dominated by a moral purpose. This dominating moral purpose in the Ideas is the highest Idea of all, the Idea of the Good, which stands above all the others and gives to them and to everything else their value and indeed their actuality.

Is this Idea of the Good the same as God? Plato calls the Good “Deity” and the “World Reason,” and ascribes to it the name of Nous. Nevertheless the Idea of the Good is not the same as the Christian God, and Plato is only showing here the influence of Anaxagoras’ conception upon him. (See p. [47].) The Idea of the Good is not a person or a spiritual being. It is merely the absolute ethical end and purpose of the world. Plato did not attempt to give it a content, any more than did his master, Socrates; but Plato presupposed it, because it was in itself the simplest and most comprehensible thing in the world.

Plato’s Conception of Physical Nature. Plato constructed a rough sketch of the philosophy of nature in his later years, in compliance with the needs of his School, and perhaps with the urging of his pupil, Aristotle. In his earlier period, he would have nothing of physics, and was in this respect quite in accord with the spirit of Socrates. To the end of his life he maintained that there can be no true knowledge of the physical world; for it is a world of change, and therefore all scientific conclusions about it could be only probable. In a mythical account in the Timæus he drew a picture of the constitution of the world. He conceived a Demiurge or world-forming God to exist, and he thought that this God made the world out of not-Beingor empty space “with regard to the Ideas.” The world thus constructed is conceived by Plato as a huge living thing, composed of a visible body and an invisible soul. The world-soul sets the world-body in a circular motion, which motion was considered by antiquity to be the most perfect of all motions. In sharp opposition to the mechanical theory of the world, Plato conceived the world to be endowed with knowledge, of which the spherical motion in its return upon itself is the symbol. The world is unitary and unique, the most perfect and most beautiful world, and its origin can be traced only to a reason working toward ends. Plato’s physics, of which the above is an abbreviated account, will be seen to be of little importance; but it was unfortunately, as we have said, this side of his doctrine that was emphasized in the Middle Ages.

This mythical account shows, however, the inherent dualism in Plato’s doctrine. The Idea never fully realizes itself in corporeal things, and Plato was called on to explain the cause of the evil and imperfection of the physical world. Moreover, the imperfection of the physical world got new emphasis in the influence upon him of the Pythagorean doctrine, which had set the perfect and imperfect worlds in opposition. What prevents the Idea from fully appearing in phenomena? The more Plato conceived the world of Ideas as ethical Ideals and a kingdom of pure worth, and the more teleological the Ideas became, the less could he regard the Ideas as the cause of imperfection in nature. Ideas are Being, and the essence of perfection. The cause of imperfection must therefore be that which has no being whatsoever. The physical world as “becoming” has participation, not only in that which has Being (Ideas),but in that which has no Being (empty space). The physical world has a composite character. It has sprung from the union of the Ideas and an absolutely negative factor, which Plato calls empty space. This eternal negative is formless and unfashioned, but it is capable of taking on all possible forms. The physical universe is therefore neither Ideas simply, nor matter simply, but a composition of the two. This non-Being is not like the matter, “unformed stuff,” of Aristotle, from which all sensible things are made; but it is that in which Ideas have to appear. The Ideas are plunged into this empty non-Being, which they take on as a veil. And just this is the origin of imperfection; non-Being withholds the Ideas from perfect expression. Non-Being, or empty space, is an indispensable auxiliary to the Ideas, for without it no physical universe would be possible. But at the same time it is the eternal foe and obstruction of the Ideas. Its coöperation with the Ideas is at the same time a resistance to them. It is the perpetual negation of Being, and the primary cause of imperfection, change, and instability. On this account the universe can never be like the Ideas, but it can approximate them. The soul of the world, for example,—which was regarded by Plato in Pythagorean fashion as number subjecting chaotic space to harmony,—is the most perfect reproduction of the Idea of the Good. The existence of matter detracts from the perfection of the world, but it does not detract from the majesty of the Ideas.

Plato’s Conception of Man. Plato needed a psychology of another sort from that developed by the Cosmologists. His analysis of the mental life of man stands or falls with his metaphysical theory of Ideas, but ithas this importance: it is the first attempt to understand the psychical life from within.

The dualism of the two worlds appears in sharp outlines in the narrower field of the life of man. The soul of man belongs to both worlds. On the one hand, it belongs to the world of Becoming and partakes of that world through its sense-perceptions, desires, and their pleasures. In this lower world it is the principle of life and motion; it is that which moves itself and other things. On the other hand, it shares in the world of Being through its intuitive reason or knowledge. It shares in the instability and change of psychical phenomena; it also possesses the immutability of reality. Through its perceptions it constructs its “opinions” or inferences of changing phenomena; through its reason it has true knowledge of the eternal Ideas. Therefore the soul must bear in itself traits that correspond to the two worlds. Plato conceives man to have an irrational and a rational nature; and he divides the irrational nature into two parts,—the noble irrational part and the ignoble irrational part. The rational part of man is the reason, the noble irrational part is the will, the ignoble irrational part is the sensuous appetites.