A more thorough explanation:

Definition: Pure theory is a legal philosophy developed by Hans Kelsen. According to Kelsen, a legal system must be "pure," meaning it should be self-supporting and not dependent on external values. In his theory, laws are norms created by the state and are not defined by history, ethics, sociology, or other external factors. A legal system is an interconnected system of norms, and each law's validity is traced to another legal norm. Ultimately, all laws must find their validity in the society's basic norm (grundnorm).

Example: An example of a norm is the standard for right or wrong behavior. For instance, in some societies, it is considered wrong to eat with your left hand, while in others, it is acceptable. In Kelsen's pure theory, the validity of a law is not determined by whether it is right or wrong but by its connection to other legal norms and the society's basic norm.

Explanation: Kelsen's pure theory emphasizes that a legal system should be self-sufficient and not dependent on external values. The example of a norm illustrates how different societies have different standards for right or wrong behavior, which may not be relevant in a legal system. Instead, Kelsen's theory suggests that the validity of a law should be determined by its connection to other legal norms and the society's basic norm.