In this Article, I argue that legal positivism is subject to the same paradox as was engendered by Frege's set theory-a paradox that has come to be known as Russell's Paradox. Basically, Frege tried to define what a set is. Russell showed that, because of self-reference, any attempt to define the word "set" led to formal condition. I argue that Russell's analysis can be applied to legal positivism, if "legal positivism" is defined to mean that a complete and closed rule of recognition for law is a logical possibility. I also argue that, to the extent legal positivism claims that law is not necessarily related to morality, then legal positivism is committed to the claim that there is a determinate rule of recognition. Only then can one be sure that a given law is purely a legal rule and not a moral rule. Because of the paradox, it is not logically coherent to divorce law and morality entirely, because no final and complete rule of recognition can possibly exist.