Morality

"In trying to provide a definition of what I take to be the ordinary normative sense of “morality,” that is, a moral system that is put forward by rational persons to be used by all moral agents in guiding their conduct, I find it useful to regard morality as a public system. I use the phrase, “public system” to refer to a guide to conduct such that (1) all persons to whom it applies, all those whose behavior is to be guided and judged by that system, know what behavior the system prohibits, requires, discourages, encourages, and allows; and (2) it is not irrational for any of these persons to accept being guided and judged by that system. What this means is that insofar as a person is legitimately ignorant of what he is morally prohibited or required to do, he is not subject to moral judgment. This is one way in which morality in the normative sense differs from law. Law is not a public system for sometimes “ignorance of the law provides no excuse.” Even if a person is legitimately ignorant of what he is legally prohibited or required to do, he may still be subject to legal judgment" - http://plato.stanford.edu/entries/morality-definition/