17. Living in an age when logic was beginning to mould human thought, Plato naturally cast his belief in immortality into a logical form. And when we consider how much the doctrine of ideas was also one of words, it is not surprising that he should have fallen into verbal fallacies: early logic is always mistaking the truth of the form for the truth of the matter. It is easy to see that the alternation of opposites is not the same as the generation of them out of each other; and that the generation of them out of each other, which is the first argument in the Phaedo, is at variance with their mutual exclusion of each other, whether in themselves or in us, which is the last. For even if we admit the distinction which he draws between the opposites and the things which have the opposites, still individuals fall under the latter class; and we have to pass out of the region of human hopes and fears to a conception of an abstract soul which is the impersonation of the ideas. Such a conception, which in Plato himself is but half expressed, is unmeaning to us, and relative only to a particular stage in the history of thought. The doctrine of reminiscence is also a fragment of a former world, which has no place in the philosophy of modern times. But Plato had the wonders of psychology just opening to him, and he had not the explanation of them which is supplied by the analysis of language and the history of the human mind. The question, ‘Whence come our abstract ideas?’ he could only answer by an imaginary hypothesis. Nor is it difficult to see that his crowning argument is purely verbal, and is but the expression of an instinctive confidence put into a logical form:—’The soul is immortal because it contains a principle of imperishableness.’ Nor does he himself seem at all to be aware that nothing is added to human knowledge by his ‘safe and simple answer,’that beauty is the cause of the beautiful; and that he is merely reasserting the Eleatic being ‘divided by the Pythagorean numbers,’ against the Heracleitean doctrine of perpetual generation. The answer to the ‘very serious question’ of generation and destruction is really the denial of them. For this he would substitute, as in the Republic, a system of ideas, tested, not by experience, but by their consequences, and not explained by actual causes, but by a higher, that is, a more general notion. Consistency with themselves is the only test which is to be applied to them. (Republic, and Phaedo.)