There are (apart from the world as a whole) four kinds of animals: gods, birds, fishes, and land animals. The gods are mainly fire; the fixed stars are divine and eternal animals. The Creator told the gods that he could destroy them, but would not do so. He left it to them to make the mortal part of all other animals, after he had made the immortal and divine part. (This, like other passages about the gods in Plato, is perhaps not to be taken very seriously. At the beginning, Timaeus says he seeks only probability, and cannot be sure. Many details are obviously imaginative, and not meant literally.)
The Creator, Timaeus says, made one soul for each star. Souls have sensation, love, fear, and anger; if they overcome these, they live righteously, but if not, not. If a man lives well, he goes, after death, to live happily for ever in his star. But if he lives badly, he will, in the next life, be a woman; if he (or she) persists in evil-doing, he (or she) will become a brute, and go on through transmigrations until at last reason conquers. God put some souls on earth, some on the moon, some on other planets and stars, and left it to the gods to fashion their bodies.
There are two kinds of causes, those that are intelligent, and those that, being moved by others, are, in turn, compelled to move others. The former are endowed with mind, and are the workers of things fair and good, while the latter produce chance effects without order or design. Both sorts ought to be studied, for the creation is mixed, being made up of necessity and mind. (It will be observed that necessity is not subject to God’s power.) Timaeus now proceeds to deal with the part contributed by necessity.
Earth, air, fire, and water are not the first principles or letters or elements; they are not even syllables or first compounds. Fire, for instance, should not be called this, but such—that is to say, it is not a substance, but rather a state of substance. At this point, the question is raised: Are intelligible essences only names? The answer turns, we are told, on whether mind is or is not the same thing as true opinion. If it is not, knowledge must be knowledge of essences, and therefore essences cannot be mere names. Now mind and true opinion certainly differ, for the one is implanted by instruction, the other by persuasion; one is accompanied by true reason, the other is not; all men share in true opinion, but mind is the attribute of the gods and of a very few among men.
This leads to a somewhat curious theory of space, as something intermediate between the world of essence and the world of transient sensible things.
There is one kind of being which is always the same, uncreated and indestructible, never receiving anything into itself from without, nor itself going out to any other, but invisible and imperceptible by any sense, and of which the contemplation is granted to intelligence only. And there is another nature of the same name with it, and like to it, perceived by sense, created, always in motion, becoming in place and again vanishing out of place, which is apprehended by opinion and sense. And there is a third nature, which is space, and is eternal, and admits not of destruction and provides a home for all created things, and is apprehended without the help of sense, by a kind of spurious reason, and is hardly real; which we beholding as in a dream, say of all existence that it must of necessity be in some place and occupy a space, but that what is neither in heaven nor on earth has no existence.
This is a very difficult passage, which I do not pretend to understand at all fully. The theory expressed must, I think, have arisen from reflection on geometry, which appeared to be a matter of pure reason, like arithmetic, and yet had to do with space, which was an aspect of the sensible world. In general it is fanciful to find analogies with later philosophers, but I cannot help thinking that Kant must have liked this view of space, as one having an affinity with his own.
The true elements of the material world, Timaeus says, are not earth, air, fire, and water, but two sorts of right-angled triangles, the one which is half a square and the one which is half an equilateral triangle. Originally everything was in confusion, and “the various elements had different places before they were arranged so as to form the universe.” But then God fashioned them by form and number, and “made them as far as possible the fairest and best, out of things which were not fair and good.” The above two sorts of triangles, we are told, are the most beautiful forms, and therefore God used them in constructing matter. By means of these two triangles, it is possible to construct four of the five regular solids, and each atom of one of the four elements is a regular solid. Atoms of earth are cubes; of fire, tetrahedra; of air, octahedra; and of water, icosahedra. (I shall come to the dodecahedron presently.)
The theory of the regular solids, which is set forth in the thirteenth book of Euclid, was, in Plato’s day, a recent discovery; it was completed by Theaetetus, who appears as a very young man in the dialogue that bears his name. It was, according to tradition, he who first proved that there are only five kinds of regular solids, and discovered the octahedron and the icosahedron.* The regular tetrahedron, octahedron, and icosahedron, have equilateral triangles for their faces; the dodecahedron has regular pentagons, and cannot therefore be constructed out of Plato’s two triangles. For this reason he does not use it in connection with the four elements.
As for the dodecahedron, Plato says only “there was yet a fifth combination which God used in the delineation of the universe.” This is obscure, and suggests that the universe is a dodecahedron; but elsewhere it is said to be a sphere. The pentagram has always been prominent in magic, and apparently owes this position to the Pythagoreans, who called it “Health” and used it as a symbol of recognition of members of the brotherhood.† It seems that it owed its properties to the fact that the dodecahedron has pentagons for its faces, and is, in some sense, a symbol of the universe. This topic is attractive, but it is difficult to ascertain much that is definite about it.
After a discussion of sensation, Timaeus proceeds to explain the two souls in man, one immortal, the other mortal, one created by God, the other by the gods. The mortal soul is “subject to terrible and irresistible affections—first of all, pleasure, the greatest incitement to evil; then pain, which deters from good; also rashness and fear, two foolish counsellors, anger hard to be appeased, and hope easily led astray; these they (the gods) mingled with irrational sense and with all-daring love according to necessary laws, and so framed men.”
The immortal soul is in the head, the mortal in the breast.
There is some curious physiology, as, that the purpose of the intestines is to prevent gluttony by keeping the food in, and then there is another account of transmigration. Cowardly or unrighteous men will, in the next life, be women. Innocent light-minded men, who think that astronomy can be learnt by looking at the stars without knowledge of mathematics, will become birds; those who have no philosophy will become wild land-animals; the very stupidest will become fishes.
The last paragraph of the dialogue sums it up:
We may now say that our discourse about the nature of the universe has an end. The world has received animals, mortal and immortal, and is fulfilled with them, and has become a visible animal containing the visible—the sensible God who is the image of the intellectual, the greatest, best, fairest, most perfect—the one only-begotten heaven.
It is difficult to know what to take seriously in the Timaeus, and what to regard as play of fancy. I think the account of the creation as bringing order out of chaos is to be taken quite seriously; so also is the proportion between the four elements, and their relation to the regular solids and their constituent triangles. The accounts of time and space are obviously what Plato believes, and so is the view of the created world as a copy of an eternal archetype. The mixture of necessity and purpose in the world is a belief common to practically all Greeks, long antedating the rise of philosophy; Plato accepted it, and thus avoided the problem of evil, which troubles Christian theology. I think his world-animal is seriously meant. But the details about transmigration, and the part attributed to the gods, and other inessentials, are, I think, only put in to give a possible concreteness.
The whole dialogue, as I said before, deserves to be studied because of its great influence on ancient and medieval thought; and this influence is not confined to what is least fantastic.
CHAPTER XVIII
Knowledge and Perception in Plato
MOST modern men take it for granted that empirical knowledge is dependent upon, or derived from, perception. There is, however, in Plato and among philosophers of certain other schools, a very different doctrine, to the effect that there is nothing worthy to be called “knowledge” to be derived from the senses, and that the only real knowledge has to do with concepts. In this view, “ 2 + 2 = 4” is genuine knowledge, but such a statement as “snow is white” is so full of ambiguity and uncertainty that it cannot find a place in the philosopher’s corpus of truths.
This view is perhaps traceable to Parmenides, but in its explicit form the philosophic world owes it to Plato. I propose, in this chapter, to deal only with Plato’s criticism of the view that knowledge is the same thing as perception, which occupies the first half of the Theaetetus.
This dialogue is concerned to find a definition of “knowledge,” but ends without arriving at any but a negative conclusion; several definitions are proposed and rejected, but no definition that is considered satisfactory is suggested.
The first of the suggested definitions, and the only one that I shall consider, is set forth by Theaetetus in the words:
“It seems to me that one who knows something is perceiving the thing that he knows, and, so far as I can see at present, knowledge is nothing but perception.”
Socrates identifies this doctrine with that of Protagoras, that “man is the measure of all things,” i.e. that any given thing “is to me such as it appears to me, and is to you such as it appears to you.” Socrates adds: “Perception, then, is always something that is, and, as being knowledge, it is infallible.”
A large part of the argument that follows is concerned with the characterization of perception; when once this is completed, it does not take long to prove that such a thing as perception has turned out to be cannot be knowledge.
Socrates adds to the doctrine of Protagoras the doctrine of Heraclitus, that everything is always changing, i.e. that “all the things we are pleased to say ‘are’ really are in process of becoming.” Plato believes this to be true of objects of sense, but not of the objects of real knowledge. Throughout the dialogue, however, his positive doctrines remain in the background.
From the doctrine of Heraclitus, even if it be only applicable, to objects of sense, together with the definition of knowledge as perception, it follows that knowledge is of what becomes, not of what is.
There are, at this point, some puzzles of a very elementary character. We are told that, since 6 is greater than 4 but less than 12, 6 is both great and small, which is a contradiction. Again, Socrates is now taller than Theaetetus, who is a youth not yet full grown; but in a few years Socrates will be shorter than Theaetetus. Therefore Socrates is both tall and short. The idea of a relational proposition seems to have puzzled Plato, as it did most of the great philosophers down to Hegel (inclusive). These puzzles, however, are not very germane to the argument, and may be ignored.
Returning to perception, it is regarded as due to an interaction between the object and the sense-organ, both of which, according to the doctrine of Heraclitus, are always changing, and both of which, in changing, change the percept. Socrates remarks that when he is well he finds wine sweet, but when ill, sour. Here it is a change in the percipient that causes the change in the percept.
Certain objections to the doctrine of Protagoras are advanced, and some of these are subsequently withdrawn. It is urged that Protagoras ought equally to have admitted pigs and baboons are measures of all things, since they also are percipients. Questions are raised as to the validity of perception in dreams and in madness. It is suggested that, if Protagoras is right, one man knows no more than another: not only is Protagoras as wise as the gods, but, what is more serious, he is no wiser than a fool. Further, if one man’s judgements are as correct as another’s, the people who judge that Protagoras is mistaken have the same reason to be thought right as he has.
Socrates undertakes to find an answer to many of these objections, putting himself, for the moment, in the place of Protagoras. As for dreams, the percepts are true as percepts. As for the argument about pigs and baboons, this is dismissed as vulgar abuse. As for the argument that, if each man is the measure of all things, one man is as wise as another, Socrates suggests, on behalf of Protagoras, a very interesting answer, namely that, while one judgement cannot be truer than another, it can be better, in the sense of having better consequences. This suggests pragmatism.*
This answer, however, though Socrates has invented it, does not satisfy him. He urges, for example, that when a doctor foretells the course of my illness, he actually knows more of my future than I do. And when men differ as to what it is wise for the State to decree, the issue shows that some men had a greater knowledge as to the future than others had. Thus we cannot escape the conclusion that a wise man is a better measure of things than a fool.
All these are objections to the doctrine that each man is the measure of all things, and only indirectly to the doctrine that “knowledge” means “perception,” in so far as this doctrine leads to the other. There is, however, a direct argument, namely that memory must be allowed as well as perception. This is admitted, and to this extent the proposed definition is amended.
We come next to criticisms of the doctrine of Heraclitus. This is first pushed to extremes, in accordance, we are told, with the practice of his disciples among the bright youths of Ephesus. A thing may change in two ways, by locomotion, and by a change of quality, and the doctrine of flux is held to state that everything is always changing in both respects.† And not only is everything always undergoing some qualitative change, but everything is always changing all its qualities—so, we are told, clever people think at Ephesus. This has awkward consequences. We cannot say “this is white,” for if it was white when we began speaking it will have ceased to be white before we end our sentence. We cannot be right in saying we are seeing a thing, for seeing is perpetually changing into not-seeing.* If everything is changing in every kind of way, seeing has no right to be called seeing rather than not-seeing, or perception to be called perception rather than not-perception. And when we say “perception is knowledge,” we might just as well say “perception is not-knowledge.”
What the above argument amounts to is that, whatever else may be in perpetual flux, the meanings of words must be fixed, at least for a time, since otherwise no assertion is definite, and no assertion is true rather than false. There must be something more or less constant, if discourse and knowledge are to be possible. This, I think, should be admitted. But a great deal of flux is compatible with this admission.
There is, at this point, a refusal to discuss Parmenides, on the ground that he is too great and grand. He is a “reverend and awful figure.” “There was a sort of depth in him that was altogether noble.” He is “one being whom I respect above all.” In these remarks Plato shows his love for a static universe, and his dislike of the Heraclitean flux which he has been admitting for the sake of argument. But after this expression of reverence he abstains from developing the Parmenidean alternative to Heraclitus.
We now reach Plato’s final argument against the identification of knowledge with perception. He begins by pointing out that we perceive through eyes and ears, rather than with them, and he goes on to point out that some of our knowledge is not connected with any sense-organ. We can know, for instance, that sounds and colours are unlike, though no organ of sense can perceive both. There is no special organ for “existence and non-existence, likeness and unlikeness, sameness and differences, and also unity and numbers in general.” The same applies to honourable and dishonourable, and good and bad. “The mind contemplates some things through its own instrumentality, others through the bodily faculties.”
We perceive hard and soft through touch, but it is the mind that judges that they exist and that they are contraries. Only the mind can reach existence, and we cannot reach truth if we do not reach existence. It follows that we cannot know things through the senses alone, since through the senses alone we cannot know that things exist. Therefore knowledge consists in reflection, not in impressions, and perception is not knowledge, because it “has no part in apprehending truth, since it has none in apprehending existence.”
To disentangle what can be accepted from what must be rejected in this argument against the identification of knowledge with perception is by no means easy. There are three inter-connected theses that Plato discusses, namely:
(1) Knowledge is perception;
(2) Man is the measure of all things;
(3) Everything is in a state of flux.
(1) The first of these, with which alone the argument is primarily concerned, is hardly discussed on its own account except in the final passage with which we have just been concerned. Here it is argued that comparison, knowledge of existence, and understanding of number, are essential to knowledge, but cannot be included in perception since they are not effected through any sense-organ. The things to be said about these are different. Let us begin with likeness and unlikeness.
That two shades of colour, both of which I am seeing, are similar or dissimilar as the case may be, is something which I, for my part, should accept, not indeed as a “percept,” but as a “judgement of perception.” A percept, I should say, is not knowledge, but merely something that happens, and that belongs equally to the world of physics and to the world of psychology. We naturally think of perception, as Plato does, as a relation between a percipient and an object: we say “I see a table.” But here “I” and “table” are logical constructions. The core of crude occurrence is merely certain patches of colour. These are associated with images of touch, they may cause words, and they may become a source of memories. The percept as filled out with images of touch becomes an “object,” which is supposed physical; the percept as filled out with words and memories becomes a “perception,” which is part of a “subject” and is considered mental. The percept is just an occurrence, and neither true nor false; the percept as filled out with words is a judgement, and capable of truth or falsehood. This judgement I call a “judgement of perception.” The proposition “knowledge is perception” must be interpreted as meaning “knowledge is judgements of perception.” It is only in this form that it is grammatically capable of being correct.
A History of Western Philosophy Page 20