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would be utterly unsuited to our needs. We need plastic conceptions that can adjust themselves to the dynamic nature of reality, and, in Plato’s parlance, can know the ‘flux.’ It is only in unmeaning tautologies that the ‘ideas’ remain immobile even in the single judgment. In all real knowing subject and predicate always have their meaning changed by being combined in a judgment, alike whether this growth enriches only the mind of a single knower or extends to all those who are interested in the advancement of human knowledge. All our concepts, therefore, as James says, are teleological weapons of the human mind.
Plato, doubtless, would never have admitted that such mere instruments of human knowing were true ‘Ideas’. But neither he nor any of his many followers has ever been able to devise a tenable formula to express the (unthinkable) relation of the plastic ‘Ideas’ we use to the immutable ‘Ideas’ they have vainly postulated. Hence though we may be glad that he has expressed for all time the perfect exemplar of the rationalistic temper, we cannot in these days imitate his superb fidelity to an impracticable ideal. The growth of Science and the application of Knowledge to Life are too stupendous facts to be ignored even in the seclusion of academic lecture-rooms. And so, though philosophers as a body will naturally be the last persons to admit it, it must eventually be recognized that Protagoras’s vision of a Truth that did not shun commerce with man was truer than Plato’s dream of an Eternal Order that transcends all human understanding.