657. Anyone can see by reason that evil and faith in the one true God cannot co-exist. For evil is opposed to God, and faith is in favour of God. Evil has to do with the will and faith with thought, and the will acts upon the understanding and makes it think, but the reverse does not happen. The understanding merely tells one what one should will and do. The good therefore such a person does is essentially evil. It is like a clean bone with a rotten marrow. It is like an actor upon the stage who plays the part of an important person. And it is like the attractive face of a worn-out prostitute. It is like the butterfly flying on silvery wings to lay its tiny eggs on the leaves of a useful tree, with the result that all its fruit is lost. It is like fragrant smoke from a poisonous herb. Indeed, it is like a sermonising robber or a pious toady. His good therefore, which is essentially evil, is kept indoors in a room, while his faith, which strolls about the hall and reasons, is nothing but a chimera, a ghost or a bubble. These comparisons make plain the truth of the proposition that it is faith which is the deciding factor, according to whether it combines with good or evil.