Socrates attempts to support his view of the ideas by the parallel of the day, which is one and in many places; but he is easily driven from his position by a counter illustration of Parmenides, who compares the idea of greatness to a sail. He truly explains to Socrates that he has attained the conception of ideas by a process of generalization. At the same time, he points out a difficulty, which appears to be involved--viz. that the process of generalization will go on to infinity. Socrates meets the supposed difficulty by a flash of light, which is indeed the true answer 'that the ideas are in our minds only.' Neither realism is the truth, nor nominalism is the truth, but conceptualism; and conceptualism or any other psychological theory falls very far short of the infinite subtlety of language and thought. But the realism of ancient philosophy will not admit of this answer, which is repelled by Parmenides with another truth or half-truth of later philosophy, 'Every subject or subjective must have an object.' Here is the great though unconscious truth (shall we say?) or error, which underlay the early Greek philosophy. 'Ideas must have a real existence;' they are not mere forms or opinions, which may be changed arbitrarily by individuals. But the early Greek philosopher never clearly saw that true ideas were only universal facts, and that there might be error in universals as well as in particulars. Socrates makes one more attempt to defend the Platonic Ideas by representing them as paradigms; this is again answered by the 'argumentum ad infinitum.' We may remark, in passing, that the process which is thus described has no real existence. The mind, after having obtained a general idea, does not really go on to form another which includes that, and all the individuals contained under it, and another and another without end. The difficulty belongs in fact to the Megarian age of philosophy, and is due to their illogical logic, and to the general ignorance of the ancients respecting the part played by language in the process of thought. No such perplexity could ever trouble a modern metaphysician, any more than the fallacy of 'calvus' or 'acervus,' or of 'Achilles and the tortoise.' These 'surds' of metaphysics ought to occasion no more difficulty in speculation than a perpetually recurring fraction in arithmetic.