Of course, as Aristotle admits, there is this half truth lying at the root of the Socratic identification of virtue and knowledge that every vicious person is ignorant of what he ought to do and what he ought to abstain from doing in the sense that what he is about to do could not be defended upon any ground of enlightened self-interest. And so, while he finds sin sweet and evil pleasant, these are delusive experiences, which, if he saw life steadily and whole, he would know as such. But one reason for this ignorance is unwillingness to know. Good men do evil, and understanding men sin, partly because they are misled by false ideas, partly, also, because, knowing them false, they cannot or will not give them up. This is what Goethe very well understood when he said, "Most men prefer error to truth, because truth imposes limitations and error does not." And another reason is that when men do know, they find a deadly and mysterious, a sort of perverted joy--a sweet and terrible and secret delight,--in denying their own understanding. Thus right living calls for a repeated and difficult exercise of the will, what Professor Babbitt calls "a pulling back of the impulse to the track that knowledge indicates." Such moral mastery is not identical with moral perception and most frequently is not its accompaniment, unless observation and experience are alike fallacious. Thus the whole argument falls to the ground when we confess that possession of knowledge does not guarantee the application of it. Therefore the two things, knowledge and virtue, according to universal experience, are not identical. Humanists indeed use the word "knowledge" for the most part in an esoteric sense. Knowledge is virtue in the sense that it enables us to see virtue as excellent and desirable; it is not virtue in the sense that it alone enables us to acquire it.