 Kripke put forth what has come to be known as "the modal argument" (or "argument from rigidity").Consider the name "Aristotle" and the descriptions "the greatest student of Plato", "the founder of logic" and "the teacher of Alexander".Aristotle obviously satisfies all of the descriptions (and many of the others we commonly associate with him), but it is not necessarily true that if Aristotle existed then Aristotle was any one, or all, of these descriptions.