I’ve just been teaching Kantian ethics. The idea is that a right action is one the guiding maxim of which can be universalized without contradiction, and a wrong action is one that cannot be so universalized. So it is wrong to break your promises because if everyone did so there would be no institution of promising. It is contradictory to will universal promise-breaking, since there can be promises only when there is trust in them–which requires that they generally be kept. It’s a very clever idea, but one that only a rationalist philosopher could approve–that it’s actually contradictory to act immorally. The fault of the bad person is thus purely intellectual: he can’t see that his actions are guided by contradictory principles. Immorality is a form of incoherence. If only!