Mr. Adler's latest book is called Six Great Ideas-the ideas being truth, goodness, beauty, justice, equality, and liberty. One sample from the man whom Mr. Buckley introduces by saying: "He isn't a philosopher only while in his study or at his typewriter. He is as entirely a philosopher as Socrates was." MA: "In our society there are libertarians who think that liberty is the supreme value, and everyone should have as much as possible, without limit. There are egalitarians who [hold] the leveling doctrine of everyone should be equal, without any differences in degree at all.... The only correction of those two errors-the libertarian error and the egalitarian error-is to see that justice is the sovereign idea. You can't have too much justice.... Everyone should have as much freedom or liberty as justice allows, for more than that involves injury to others, and everyone should have as much equality as justice requires."