A Critical History of Greek Philosophy by W. T. Stace (the false prince series .txt) 📕

But if Plato, in answering the question, "What is knowledge?" follows implicitly the teaching of Socrates, he yet builds upon this teaching a new and wholly un-Socratic metaphysic of his own. The Socratic theory of knowledge he now converts into a theory of the nature of reality. This is the subject-matter of Dialectic.

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3. Dialectic, or the Theory of Ideas.

The concept had been for Socrates merely a rule of thought. Definitions, like guide-rails, keep thought upon the straight path; we compare any act with the definition of virtue in order to ascertain whether it is virtuous. But what was for Socrates merely regulative of thought, Plato now transforms into a metaphysical substance. His theory of Ideas is the theory of the objectivity of concepts. That the concept is not merely an idea in the mind, but something which has a reality of its own, outside and independent of the mind--this is the essence of the philosophy of Plato.

How did Plato arrive at this doctrine? It is founded upon the view that truth means the correspondence of one's ideas with the facts of existence. If I see a lake of water, and if there really is such a lake, then my idea is true. But if there is no lake, then my idea is false. It is an hallucination. Truth, according to this view, means that the thought in my mind is a copy of something outside my mind. Falsehood consists in having an idea which is not a copy of anything which really exists. Knowledge, of course, means knowledge of the truth. And when I say that a thought in my mind is knowledge, I must therefore mean that this thought is a copy of something that exists. But we have already seen that knowledge is the knowledge of concepts. And if a concept is true knowledge, it can only be true in virtue of the fact that it corresponds to an objective reality. There must, therefore, be general ideas or concepts, outside my mind. It were a contradiction to suppose, on the one hand, that the concept is true knowledge, and on the other, that it corresponds to nothing external {184} to us. This would be like saying that my idea of the lake of water is a true idea, but that no such lake really exists. The concept in my mind must be a copy of the concept outside it.

Now if knowledge by concepts is true, our experiences through sensation must be false. Our senses make us aware of many individual horses. Our intellect gives us the concept of the horse in general. If the latter is the sole truth, the former must be false. And this can only mean that the objects of sensation have no true reality. What has reality is the concept; what has no reality is the individual thing which is perceived by the senses. This and that particular horse have no true being. Reality belongs only to the idea of the horse in general.

Let us approach this theory from a somewhat different direction. Suppose I ask you the question, "What is beauty?" You point to a rose, and say, "Here is beauty." And you say the same of a woman's face, a piece of woodland scenery, and a clear moonlight night. But I answer that this is not what I want to know. I did not ask what things are beautiful, but what is beauty. I did not ask for many things, but for one thing, namely, beauty. If beauty is a rose, it cannot be moonlight, because a rose and moonlight are quite different things. By beauty we mean, not many things, but one. This is proved by the fact that we use only one word for it. And what I want to know is what this one beauty is, which is distinct from all beautiful objects. Perhaps you will say that there is no such thing as beauty apart from beautiful objects, and that, though we use one word, yet this is only a manner of {185} speech, and that there are in reality many beauties, each residing in a beautiful object. In that case, I observe that, though the many beauties are all different, yet, since you use the one word to describe them all, you evidently think that they are similar to each other. How do you know that they are similar? Your eyes cannot inform you of this similarity, because it involves comparison, and we have already seen that comparison is an act of the mind, and not of the senses. You must therefore have an idea of beauty in your mind, with which you compare the various beautiful objects and so recognise them as all resembling your idea of beauty, and therefore as resembling each other. So that there is at any rate an idea of one beauty in your mind. Either this idea corresponds to something outside you, or it does not. In the latter case, your idea of beauty is a mere invention, a figment of your own brain. If so, then, in judging external objects by your subjective idea, and in making it the standard of whether they are beautiful or not, you are back again at the position of the Sophists. You are making yourself and the fancies of your individual brain the standard of external truth. Therefore, the only alternative is to believe that there is not only an idea of beauty in your mind, but that there is such a thing as the one beauty itself, of which your idea is a copy. This beauty exists outside the mind, and it is something distinct from all beautiful objects.

What has been said of beauty may equally be said of justice, or of goodness, or of whiteness, or of heaviness. There are many just acts, but only one justice, since we use one word for it. This justice must be a real thing, distinct from all particular just acts. Our ideas of justice {186} are copies of it. So also there are many white objects, but also the one whiteness.

Of the above examples, several are very exalted moral ideas, such as beauty, justice, and goodness. But the case of whiteness will serve to show that the theory attributes reality not only to exalted ideas, but to others also. In fact, we might quite well substitute evil for goodness, and all the same arguments would apply. Or we might take a corporeal object such as the horse, and ask what "horse" means. It does not mean the many individual horses, for since one word is used it must mean one thing, which is related to individual horses, just as whiteness is related to individual white things. It means the universal horse, the idea of the horse in general, and this, just as much as goodness or beauty, must be something objectively real.

Now beauty, justice, goodness, whiteness, the horse in general, are all concepts. The idea of beauty is formed by including what is common to all beautiful objects, and excluding those points in which they differ. And this, as we have seen, is just what is meant by a concept. Plato's theory, therefore, is that concepts are objective realities. And he gives to these objective concepts the technical name Ideas. This is his answer to the chief question of philosophy, namely, what, amid all the appearances and unrealities of things, is that absolute and ultimate reality, from which all else is to be explained? It consists, for Plato, in Ideas.

Let us see next what the characteristics of the Ideas are. In the first place, they are substances. Substance is a technical term in philosophy, but its philosophical meaning is merely a more consistent development of its {187} popular meaning. In common talk, we generally apply the word substance to material things such as iron, brass, wood, or water. And we say that these substances possess qualities. For example, hardness and shininess are qualities of the substance iron. The qualities cannot exist apart from the substances. They do not exist on their own account, but are dependent on the substance. The shininess cannot exist by itself. There must be a shiny something. But, according to popular ideas, though the qualities are not independent of the substance, the substance is independent of the qualities. The qualities derive their reality from the substance. But the substance has reality in itself. The philosophical use of the term substance is simply a more consistent application of this idea. Substance means, for the philosopher, that which has its whole being in itself, whose reality does not flow into it from anything else, but which is the source of its own reality. It is self-caused, and self-determined. It is the ground of other things, but itself has no ground except itself. For example, if we believe the popular Christian idea that God created the world, but is Himself an ultimate and uncreated being, then, since the world depends for its existence upon God, but God's existence depends only upon Himself, God is a substance and the world is not. In this sense the word is correctly used in the Creed where it speaks of God as "three persons, but one substance." Again, if, with the Idealists, we think that mind is a self-existent reality, and that matter owes its existence to mind, then in that case matter is not substance, but mind is. In this technical sense the Ideas are substances. They are absolute and ultimate realities. {188} Their whole being is in themselves. They depend on nothing, but all things depend on them. They are the first principles of the universe.

Secondly, the Ideas are universal. An Idea is not any particular thing. The Idea of the horse is not this or that horse. It is the general concept of all horses. It is the universal horse. For this reason the Ideas are, in modern times, often called "universals."

Thirdly, the Ideas are not things, but thoughts. There is no such thing as the horse-in-general. If there were, we should be able to find it somewhere, and it would then be a particular thing instead of a universal. But in saying that the Ideas are thoughts, there are two mistakes to be carefully avoided. The first is to suppose that they are the thoughts of a person, that they are your thoughts or my thoughts. The second is to suppose that they are thoughts in the mind of God. Both these views are wrong. It would be absurd to suppose that our thoughts can be the cause of the universe. Our concepts are indeed copies of the Ideas, but to confuse them with the Ideas themselves is, for Plato, as absurd as to confuse our idea of a mountain with the mountain itself. Nor are they the thoughts of God. They are indeed sometimes spoken of as the "Ideas in the divine mind." But this is only a figurative expression. We can, if we like, talk of the sum of all the Ideas as constituting the "divine mind." But this means nothing in particular, and is only a poetical phrase. Both these mistakes are due to the fact that we find it difficult to conceive of thoughts without a thinker. This, however, is just what Plato meant. They are not subjective ideas, that is, the ideas in a particular and existent {189} mind. They are objective Ideas, thoughts which have reality on their own account, independently of any mind.

Fourthly, each Idea is a unity. It is the one amid the many. The Idea of man is one, although individual men are many. There cannot be more than one Idea for each class of objects. If there were several Ideas of justice, we should have to seek for the common element among them, and this common element would itself constitute