 Third, Ross denied that propositions regarding all-things-considered duties in particular cases are self-evident. Indeed, he denied that one can know what one’s all-things-considered duty is in any actual case; he held that this was a matter of “probable opinion”. In Ross’s view, a prima facie duty results from some one property of an action, e.g., that it is a promise keeping or that it benefits some person. But one’s all-things-considered duty results from the entire nature of an action. So one reason we cannot know our all-things-considered duty is that we cannot know whether we have identified all the features of an action that are morally relevant. And even if we could, there is the additional problem that prima facie duties can conflict, and it is not self-evident how such conflicts should be resolved.