Connected with this is another curious view of Plato’s, that knowledge and opinion must be concerned with different subject-matters. We should say: If I think it is going to snow, that is opinion; if later I see it snowing, that is knowledge; but the subject-matter is the same on both occasions. Plato, however, thinks that what can at any time be a matter of opinion can never be a matter of knowledge. Knowledge is certain and infallible; opinion is not merely fallible, but is necessarily mistaken, since it assumes the reality of what is only appearance. All this repeats what had been said by Parmenides.
There is one respect in which Plato’s metaphysic is apparently different from that of Parmenides. For Parmenides there is only the One; for Plate, there are many ideas. There are not only beauty, truth, and goodness, but, as we saw, there is the heavenly bed, created by God; there is a heavenly man, a heavenly dog, a heavenly cat, and
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so on through a whole Noah’s ark. All this, however, seems, in the Republic, to have been not adequately thought out. A Platonic idea or form is not a thought, though it may be the object of a thought. It is difficult to see how God can have created it, since its being is timeless, and he could not have decided to create a bed unless his thought, when he decided, had had for its object that very Platonic bed which we are told he brought into existence. What is timeless must be uncreated. We come here to a difficulty which has troubled many philosophic theologians. Only the contingent world, the world in space and time, can have been created; but this is the every-day world which has been condemned as illusory and also bad. Therefore the Creator, it would seem, created only illusion and evil. Some Gnostics were so consistent as to adopt this view; but in Plato the difficulty is still below the surface, and he seems, in the Republic, to have never become aware of it.
The philosopher who is to be a guardian must, according to Plato, return into the cave, and live among those who have never seen the sun of truth. It would seem that God Himself, if He wishes to amend His creation, must do likewise; a Christian Platonist might so interpret the Incarnation. But it remains completely impossible to explain why God was not content with the world of ideas. The philosopher finds the cave in existence, and is actuated by benevolence in returning to it; but the Creator, if He created everything, might, one would think, have avoided the cave altogether.
Perhaps this difficulty arises only from the Christian notion of a Creator, and is not chargeable to Plato, who says that God did not create everything, but only what is good. The multiplicity of the sensible world, on this view, would have some other source than God. And the ideas would, perhaps, be not so much created by God as constituents of His essence. The apparent pluralism involved in the multiplicity of ideas would thus not be ultimate. Ultimately there is only God, or the Good, to whom the ideas are adjectival. This, at any rate, is a possible interpretation of Plato.
Plato proceeds to an interesting sketch of the education proper to a young man who is to be a guardian. We saw that the young man is selected for this honour on the ground of a combination of intellectual and moral qualities: he must be just and gentle, fond of learning, with a good memory and a harmonious mind. The young man
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who has been chosen for these merits will spend the years from twenty to thirty on the four Pythagorean studies: arithmetic, geometry (plane and solid), astronomy, and harmony. These studies are not to be pursued in any utilitarian spirit, but in order to prepare his mind for the vision of eternal things. In astronomy, for example, he is not to trouble himself too much about the actual heavenly bodies, but rather with the mathematics of the motion of ideal heavenly bodies. This may sound absurd to modern ears, but, strange to say, it proved to be a fruitful point of view in connection with empirical astronomy. The way this came about is curious, and worth considering.
The apparent motions of the planets, until they have been very profoundly analysed, appear to be irregular and complicated, and not at all such as a Pythagorean Creator would have chosen. It was obvious to every Greek that the heavens ought to exemplify mathematical beauty, which would only be the case if the planets moved in circles. This would be especially evident to Plato, owing to his emphasis on the good. The problem thus arose: is there any hypothesis which will reduce the apparent disorderliness of planetary motions to order and beauty and simplicity? If there is, the idea of the good will justify us in asserting this hypothesis. Aristarchus of Samos found such a hypothesis: that all the planets, including the earth, go round the sun in circles. This view was rejected for two thousand years, partly on the authority of Aristotle, who attributes a rather similar hypothesis to «the Pythagoreans» ( De Coelo, 293 a). It was revived by Copernicus, and its success might seem to justify Plato’s aesthetic bias in astronomy. Unfortunately, however, Kepler discovered that the planets move in ellipses, not in circles, with the sun at a focus, not at the centre; then Newton discovered that they do not move even in exact ellipses. And so the geometrical simplicity sought by Plato, and apparently found by Aristarchus of Samos, proved in the end illusory.
This piece of scientific history illustrates a general maxim: that any hypothesis, however absurd, may be useful in science, if it enables a discoverer to conceive things in a new way; but that, when it has served this purpose by luck, it is likely to become an obstacle to further advance. The belief in the good as the key to the scientific understanding of the world was useful, at a certain stage, in as-
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tronomy, but at every later stage it was harmful. The ethical and aesthetic bias of Plato, and still more of Aristotle, did much to kill Greek science.
It is noteworthy that modern Platonists, almost without exception, are ignorant of mathematics, in spite of the immense importance that Plato attached to arithmetic and geometry, and the immense influence that they had on his philosophy. This is an example of the evils of specialization: a man must not write on Plato unless he has spent so much of his youth on Greek as to have had no time for the things that Plato thought important.
CHAPTER XVI Plato’s Theory of Immortality
THE dialogue called after Phaedo is interesting in several respects. It purports to describe the last moments in the life of Socrates: his conversation immediately before drinking the hemlock, and after, until he loses consciousness. This presents Plato’s ideal of a man who is both wise and good in the highest degree, and who is totally without fear of death. Socrates in face of death, as represented by Plato, was important ethically, both in ancient and in modern times. What the gospel account of the Passion and the Crucifixion was for Christians, the Phaedo was for pagan or freethinking philosophers. * But the imperturbability of Socrates in his last hour is bound up with his belief in immortality, and the Phaedo is important as setting forth, not only the death of a martyr, but also many doctrines which were afterwards Christian. The theology of St. Paul and of the Fathers was largely derived from it, directly or indirectly, and can hardly be understood if Plato is ignored.
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* Even for many Christians, it is second only to the death of Christ. «There is nothing in any tragedy, ancient or modern, nothing in poetry or history (with one exception), like the last hours of Socrates in Plato.» These are the words of the Rev. Benjamin Jowett.
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An earlier dialogue, the Crito, tells how certain friends and disciples of Socrates arranged a plan by which he could escape to Thessaly. Probably the Athenian authorities would have been quite glad if he had escaped, and the scheme suggested may be assumed to have been very likely to succeed. Socrates, however, would have none of it. He contended that he had been condemned by due process of law, and that it would be wrong to do anything illegal to avoid punishment. He first proclaimed the principle which we associate with the Sermon on the Mount, that «we ought not to retaliate evil for evil to any one, whatever evil we may have suffered from him.» He then imagines himself engaged in a dialogue with the laws of Athens, in which they point out that he owes them the kind of respect that a son owes to a father or a slave to his master, but in an even higher degree; and that, moreover, every Athenian citizen
