  Kelsen rightly noticed that legal norms necessarily come in systems. There are no free-floating legal norms. If, for example, somebody suggests that “the law requires a will to be attested by two witnesses”, one should always wonder which legal system is talked about; is it US law, Canadian law, German law, or the law in some other legal system? Furthermore, legal systems are themselves organized in a hierarchical structure, manifesting a great deal of complexity but also a certain systematic unity. We talk about Canadian law, or German law, etc., not only because these are separate countries in which there is law. They are also separate legal systems, manifesting a certain cohesion and unity. This systematic unity Kelsen meant to capture by the following two postulates: