 That our responsibilities are self-evident does not entail they are obvious to everyone who reflects on them. Ross says a responsibility is self-evident ‘not in the sense that it is evident from the beginning of our lives, or as soon as we attend to the proposition for the first time, but in the sense that when we have reached sufficient mental maturity and have given sufficient attention to the proposition it is evident without any need of proof, or of evidence beyond itself. It is self-evident just as a mathematical axiom, or the validity of a form of inference, is evident’ (RG 29; also 12, 32; KT 42).