 Even though (P) is not the focus of this entry, it might be useful to review Ross’s position on it. Ross provided principles specifying various grounds of duty by using the concept of prima facie duty. Ross thought of prima facie duty as a tendency to be a duty, not as a kind of duty. He held that we have prima facie duties to keep promises and tell the truth, to provide reparation for harms we have done, to perform acts of gratitude, to insure just distributions, to benefit others, to improve ourselves, and not to harm others. He held that an act is a prima facie duty in virtue of some one component of its nature, e.g., being a promise keeping. But a given act can have more than one morally significant feature, and in virtue of some features it might be prima facie right while also being prima facie wrong in virtue of other features. Imagine a mob enforcer has taken a contract to kill someone. The act of fulfilling his contract would be a prima facie duty in virtue of keeping a promise, but it would be prima facie wrong in virtue of harming, indeed, killing, a person. The act would be wrong all-things-considered. One’s all-things-considered duty, according to Ross, is determined by the entire nature of an action. Ross held that it is not possible to provide a general ranking of prima facie duties according to their stringency, with more stringent duties always trumping less stringent duties if they conflict. And he did not think it is possible to provide any other sort of general rule for determining which prima facie duty will take precedence in cases of conflict. Therefore, even if we had a set of principles identifying every prima facie right making feature and every prima facie wrong making feature—which Ross did not claim to have provided—and even if we had complete knowledge of the non-moral features of all actions, we could not mechanically deduce which actions we would be duty bound to perform.