 Second, Ross allowed that a person might come to be justified in believing one of his general principles regarding prima facie duties via what is sometimes called “intuitive induction”. One recognizes prima facie duties in particular cases first, and then comes to apprehend the general principle. Thus, for example, one intuits in a number of particular cases where one has promised, that one has a prima facie obligation to do what one has promised, and then one “sees” that one has a prima facie obligation to keep promises. Intuitive induction is supposed to produce a priori knowledge. When one knows on the basis of an intuitive induction the justification for the general principle is not derived from one’s justifications regarding the particular cases, as one would be in a standard enumerative induction. Since Ross held that principles regarding prima facie duties are self-evident, he was committed to the claim that their justification does not depend upon anything else. So the idea must instead be that thinking about the particular cases either enables one to truly understand the general principle or is involved in giving it sufficient consideration, whereupon one comes to see that it is true.