A CRITICAL SURVEY OF RESPONSES TO
In a remarkable article, Prescott Johnson (see Bibliography) seems to succeed in showing that Plato's dialectic (in The Republic) as means to knowledge of the Good amounts to an ontological argument for the necessary existence of the Good. The lesser ideas are incapable of expressing the principle of order among themselves; in conceiving this order we are conceiving a supreme idea which therefore cannot be lacking in content for our thought. This is--says Johnson--the a posteriori element in Plato's reasoning. In effect, it is his refutation of positivism. The supreme reality is not inconceivable. (I would here depart somewhat from Johnson by remarking that the conceivability of something is a necessary, not a merely contingent or factual, truth and that it cannot, properly speaking, be known a posteriori. But I shall not attempt to relate this consideration to Plato's procedure.) The supreme reality is not to be treated as a mere hypothesis. Knowledge of it "requires no assumption," and "makes no use of images, relying on ideas only." In short this knowledge is strictly a priori. And no merely contingent existence could be thus known.