Prima Facie Obligations, Ceteris Paribus Laws in Moral Theory

Morty promises to meet a friend at the station by 3:00. On his way there, he sees a seriously injured child in an alley; and helping the child will make Morty late. Morty ought to help children in need, but he also ought to keep his promises. So it seems that Morty ought to help the child and be at the station by 3:00, even if he cannot do both. Such moral conflicts are interesting for several reasons, not least of which is that they generate now-familiar paradoxes with the following general form: