Nietzsche vs Plato

On what did these two base their philosophies? What did they see as the authority for what they had to present and on which their arguments rested?

This is a question that is not as easy as it seems. It depends first what you mean by authority. Take Christianity for instance. We might think that it was based on the ultimate authority of the life and teaching of the Lord Jesus and on the ideas He taught. Simple, is it not? No, it is not at all simple. There are plenty of organizations which claim to speak for Him. They all claim to be “God’s organization” or “the True Church” or something similar. Then there are the problems of Bible versions, each one, or rather its publisher claiming that their’s is the most accurate or closer to the original text. It is something of a joke that a man like Rupert Murdoch, the pornographer in chief, of popular tabloids, has the privilege of publishing and distributing at least one version of the Bible.

So then, if we say that Plato’s authority is “The Good” we are immediately faced with the problem of what it is that “The Good” is. Well what is it? The simple answer to that is, “I do not know,” nor it seems did Plato. If he did he is remarkable coy about defining it even though Socrates often asks his stooges for definitions. When, in The Republic, Socrates sets about finding what “justice” is, all he can give us is the example of an ideal state which we are meant to believe is a “just” society. It is “just” apparently because it is governed by philosophers who have had a vision of “The Good” and, therefore know what justice is and how to rule accordingly.

In a series of analogies Plato, through the mouthpiece of Socrates, gives us the idea of what it is and how it is found. The analogy of the “Cave” is one. People sit in darkness and look at shadows of things cast by a light behind them on the wall in front of them. If someone were to escape and to get out into the sunlight he would at first be dazzled, but then, as he grew accustomed, he would be able to see things as they really are. The climax of this is that the gifted person would, at last be able to see the sun itself, the giver of light, and this is the same as first seeing good things and then “the Good” itself. It is somewhat like a concept, but writ large.