 One issue arises with respect to Ross’s contrast between our knowledge of prima facie duties or responsibilities and our knowledge of our actual obligation in a situation. Ross thinks we have certainty with respect to prima facie responsibilities (RG 30), but only probable opinion of our actual duty. Our lack of knowledge of our actual duty is due in part to the difficulty of determining the precise weight of a prima facie duty or its degree of obligatoriness (FE 188).