Apart from The Prior Analytics, which deals with the syllogism, there are other writings of Aristotle which have considerable importance in the history of philosophy. One of these is the short work on The Categories. Porphyry the Neoplatonist wrote a commentary on this book, which had a very notable influence on medieval philosophy; but for the present let us ignore Porphyry and confine ourselves to Aristotle.
What, exactly, is meant by the word «category,» whether in Aristotle or in Kant and Hegel, I must confess that I have never been able
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to understand. I do not myself believe that the term «category» is in any way useful in philosophy, as representing any clear idea. There are, in Aristotle, ten categories: substance, quantity, quality, relation, place, time, position, state, action, and affection. The only definition offered of the term «category» is: «expressions which are in no way composite signify»—and then follows the above list. This seems to mean that every word of which the meaning is not compounded of the meanings of other words signifies a substance or a quantity or etc. There is no suggestion of any principle on which the list of ten categories has been compiled.
«Substance» is primarily what is not predicable of a subject nor present in a subject. A thing is said to be ‘present in a subject» when, though not a part of the subject, it cannot exist without the subject. The instances given are a piece of grammatical knowledge which is present in a mind, and a certain whiteness which may be present in a body. A substance in the above primary sense is an individual thing or person or animal. But in a secondary sense a species or a genus-e.g., «man» or «animal»-may be called a substance. This secondary sense seems indefensible, and opened the door, in later writers, to much bad metaphysics.
The Posterior Analytics is a work largely concerned with a question which must trouble any deductive theory, namely: How are first premisses obtained? Since deduction must start from somewhere, we must begin with something unproved, which must be known otherwise than by demonstration. I shall not give Aristotle’s theory in detail, since it depends upon the notion of essence. A definition, he says, is a statement of a thing’s essential nature. The notion of essence is an intimate part of every philosophy subsequent to Aristotle, until we come to modern times. It is, in my opinion, a hopelessly muddle-headed notion, but its historical importance requires us to say something about it.
The «essence» of a thing appears to have meant «those of its properties which it cannot change without losing its identity.» Socrates may be sometimes happy, sometimes sad; sometimes well, sometimes ill. Since he can change these properties without ceasing to be Socrates, they are no part of his essence. But it is supposed to be of the essence of Socrates that he is a man, though a Pythagorean, who believes in transmigration, will not admit this. In fact, the question of
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«essence» is one as to the use of words. We apply the same name, on different occasions, to somewhat different occurrences, which we regard as manifestations of a single «thing» or «person.» In fact, however, this is only a verbal convenience. The «essence» of Socrates thus consists of those properties in the absence of which we should not use the name «Socrates.» The question is purely linguistic: a word may have an essence, but a thing cannot.
The conception of «substance,» like that of «essence,» is a transference to metaphysics of what is only a linguistic convenience. We find it convenient, in describing the world, to describe a certain number of occurrences as events in the life of «Socrates,» and a certain number of others as events in the life of «Mr. Smith.» This leads us to think of «Socrates» or «Mr. Smith» as denoting something that persists through a certain number of years, and as in some way more «solid» and «real» than the events that happen to him. If Socrates is ill, we think that Socrates, at other times, is well, and therefore the being of Socrates is independent of his illness; illness, on the other hand, requires somebody to be ill. But although Socrates need not be ill, something must be occurring to him if he is to be considered to exist. He is not, therefore, really any more «solid» than the things that happen to him.
«Substance,» when taken seriously, is a concept impossible to free from difficulties. A substance is supposed to be the subject of properties, and to be something distinct from all its properties. But when we take away the properties, and try to imagine the substance by itself, we find that there is nothing left. To put the matter in another way: What distinguishes one substance from another? Not difference of properties, for, according to the logic of substance, difference of properties presupposes numerical diversity between the substances concerned. Two substances, therefore, must be just two, without being, in themselves, in any way distinguishable. How, then, are we ever to find out that they are two?
«Substance,» in fact, is merely a convenient way of collecting events into bundles. What can we know about Mr. Smith? When we look at him, we see a pattern of colours; when we listen to him talking, we hear a series of sounds. We believe that, like us, he has thoughts and feelings. But what is Mr. Smith apart from all these occurrences? A mere imaginary hook, from which the occurrences
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are supposed to hang. They have in fact no need of a hook, any more than the earth needs an elephant to rest upon. Any one can see, in the analogous case of a geographical region, that such a word as » France» (say) is only a linguistic convenience, and that there is not a thing called «France» over and above its various parts. The same holds of «Mr. Smith»; it is a collective name for a number of occurrences. If we take it as anything more, it denotes something completely unknowable, and therefore not needed for the expression of what we know.
«Substance,» in a word, is a metaphysical mistake, due to transference to the world-structure of the structure of sentences composed of a subject and a predicate.
I conclude that the Aristotelian doctrines with which we have been concerned in this chapter are wholly false, with the exception of the formal theory of the syllogism, which is unimportant. Any person in the present day who wishes to learn logic will be wasting his time if he reads Aristotle or any of his disciples. None the less, Aristotle’s logical writings show great ability, and would have been useful to mankind if they had appeared at a time when intellectual originality was still active. Unfortunately, they appeared at the very end of the creative period of Greek thought, and therefore came to be accepted as authoritative. By the time that logical orginality revived, a reign of two thousand years had made Aristotle very difficult to dethrone. Throughout modern times, practically every advance in science, in logic, or in philosophy has had to be made in the teeth of the opposition from Aristotle’s disciples.
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CHAPTER XXIII Aristotle’s Physics
IN this chapter I propose to consider two of Aristotle’s books, the one called Physics and the one called On the Heavens. These two books are closely connected; the second takes up the argument at the point at which the first has left it. Both were extremely influential, and dominated science until the time of Galileo. Words such as «quintessence» and «sublunary» are derived from the theories expressed in these books. The historian of philosophy, accordingly, must study them, in spite of the fact that hardly a sentence in either can be accepted in the light of modern science.
To understand the views of Aristotle, as of most Greeks, on physics, it is necessary to apprehend their imaginative background. Every philosopher, in addition to the formal system which he offers to the world, has another, much simpler, of which he may be quite unaware. If he is aware of it, he probably realizes that it won’t quite do; he therefore conceals it, and sets forth something more sophisticated, which he believes because it is like his crude system, but which he asks others to accept because he thinks he has made it such as cannot be disproved. The sophistication comes in by way of refutation of refutations, but this alone will never give a positive result: it shows, at best, that a theory may be true, not that it must be. The positive result, however little the philosopher may realize it, is due to his imaginative preconceptions, or to what Santayana calls
