The difference between Plato and Augustine on this most fundamental point of the position of God in the Ideal world may still more clearly be observed if we notice the argument each one gives for holding to his own position. Plato says that to appeal to the revelation of God is really to give up philosophy altogether. He says that we may ask the oracles of the gods when we have to give up philosophy in despair, but not till then. He would not appeal to what he considered foreign aid until his own efforts were proved useless. And even then he did not really expect any help from the ancients or from the oracles. On the other hand, Augustine is equally convinced that unless human knowledge has the right to appeal to divine knowledge, not as to a foreign something, there will be no knowledge for man. He feels that unless we can appeal to God we may as well give up philosophy. So far from subtracting from certainty of human knowledge, the appeal to divine revelation makes it all the more certain. "The ultimate ground of our certitude becomes our confidence in God. In the last analysis, God is our surety for the validity of our knowledge; and that not merely remotely, as the author of our faculties of knowing, but also immediately as the author of our every act of knowing, and the truth which is known."

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