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Statesman (283 ff.) ; a scheme of categories is found in tlie Pliilebus (p. 66) ; the true doctrine of contradiction (436 fT.) is taught, and the fallacy of arguing in a circle (p. 505) is exposed in the Republic ; the nature of synthesis and analysis is graphically described in the Phaedrus (p. 265) ; the nature of words is analysed in the Cratylus ; the form of the syllogism is indicated in the genea- logical trees of the Sophist and Statesman ; a true doctrine of predication and an analysis of the sentence are given in the Sophist (p. 262) ; the diiferent meanings of one and being are worked out in the Parmenides. Here we have most of the important elements of logic, not yet systematized or reduced to an art or science, but scattered up and down as they would naturally occur in ordinary discourse. They are of little or no use or significance to us ; but because we have grown out of the need of them we should not therefore despise them. They are still interesting and instructive for the light which they shed on the history of the human mind.

There are indeed many old fallacies which linger among us, and new ones are constantly springing up. But they are not of the kind to which ancient logic can be usefully applied. The weapons of common sense, not the analytics of Aristotle, are needed for their overthrow. Nor is the use of the Aristotelian logic any longer natural to us. We no longer put arguments into the form of syllogisms like the schoolmen ; the simple use of language has been, happily, restored to us. Neither do we discuss the nature of the proposition, nor extract hidden truths from the copula, nor dispute any longer about nominalism and realism. We do not confuse the form with the matter of knowledge, or invent laws of thought, or imagine that any single science furnishes a principle of reasoning to all the rest. Neither do we require categories or heads of argument to be invented for our use. Those who have no knowledge of logic, like some of our great physical philosophers, seem to be quite as good reasoners as those who have. Most of the ancient puzzles have been settled on the basis of usage and common sense ; there is no need to reopen them. No science should raise problems or invent forms of thought which add nothing to knowledge and are of no use in assisting the acquisition of it. This seems to be the natural limit of logic and metaphysics ; if they give us a more comprehensive or a more definite view of