As Christ's comment on the commandment indicates, the sin of lust is already "unfleshly" to the degree that it is possible to have lustful thoughts without lustful deeds, but the former are still "fleshly" in that the thinker cannot avoid knowing what they are; he may insist that his thoughts are not sinful but he cannot pretend that they are not lustful. Further, the relation between thought and act is still direct. The thought is the thought of a specific act. The lustful man cannot be a hypocrite to himself except through a symbolic transformation of his desires into images which are not consciously lustful. But the more "spiritual" the sin, the more indirect is the relationship between thought and act, and the easier it is to conceal the sin from others and oneself. I have only to watch a glutton at the dinner table to see that he is a glutton, but I may know someone for a very long time before I realize that he is an envious man, for there is no act which is in itself envious; there are only acts done in the spirit of envy, and there is often nothing about the acts themselves to show that they are done from envy and not from love. It is always possible, therefore, for the envious man to conceal from himself the fact that he is envious and to believe that he is acting from the highest of motives. While in the case of the purely spiritual sin of pride there is no "fleshly" element of the concrete whatsoever, so that no man, however closely he observes others, however strictly he examines himself, can ever know if they or he are proud; if he finds traces of any of the other six capital sins, he can infer pride, because pride is fallen "Spirit-in-itself" and the source of all the other sins, but he cannot draw the reverse inference and, because he finds no traces of the other six, say categorically that he, or another, is not proud.
If man's physical nature could speak when his spirit rebukes it for its corruption, it would have every right to say, "Well, who taught me my bad habits?"; as it is, it has only one form of protest, sickness; in the end, all it can do is destroy itself in an attempt to murder its master.
Over against Caliban, the embodiment of the natural, stands the invisible spirit of imagination, Ariel. (In a stage production, Caliban should be as monstrously conspicuous as possible, and, indeed, suggest, as far as decency permits, the phallic. Ariel, on the other hand, except when he assumes a specific disguise at Prospero's order, e.g., when he appears as a harpy, should, ideally, be invisible, a disembodied voice, an ideal which, in these days of microphones and loud-speakers, should be realizable.)