Hans Kelsen

Law is an order of human behavior. An “order” is a system of rules. Law is not, as it is sometimes said, a rule. It is a set of rules having the kind of unity we understand by a system. It is impossible to grasp the nature of law if we limit our attention to the single isolated rule.

— Hans Kelsen

It is called a “pure” theory of law, because it only describes the law and attempts to eliminate from the object of this description everything that is not strictly law: Its aim is to free the science of law from alien elements. This is the methodological basis of the theory.

— Hans Kelsen