a self-evident and necessary truth, or a proposition whose truth is so evident as first sight that no reasoning or demonstration can make it plainer; a proposition which it is necessary to take for granted; as, "the whole is greater than a part;"  "a thing can not, at the same time, be and not be."-an established principle in some art or science, which, though not a necessary truth, is universally received; as, the axioms of political economy.