Why can we not have two distinct sets of moral principles? We may, it would seem, go through life comfortably enough, pursuing happiness where possible and doing our duty when it thrusts itself on us without ever resolving in our minds the relation between the two. We do some things because we want to, others because we ought to; these two practical reasonings are different, and we hope for a life in which a certain balance can be struck between them. This view has had some recent popularity. But