an empirical origin, so far as they arise from the idea of harm done, but per se they rest on the pure understanding, which a priori furnishes ready to hand the axiom: causa causae est causa effectus. (The cause of a cause is the cause of the effect.) Taken in this connection the words mean: if any one desires to injure me, it is not I, but he, that is the cause of whatever I am obliged to do in self-defence; and I can consequently oppose all encroachments on his part, without wronging him.

Here we have, so to say, a law of moral repercussion. Thus it comes about that the union of the empirical idea of injury done with the axiom supplied by the pure understanding, gives rise to the fundamental conceptions of wrong and right, which every one grasps a priori, and learns by actual trial to immediately adopt.