  Whether these two postulates are actually true is a contentious issue. Joseph Raz argued that they are both inaccurate, at best.  Two norms can derive their validity from the same basic norm, but fail to belong to the same system as, for example, in case of an orderly secession whereby a new legal system is created by the legal authorization of another. Nor is it necessarily true that all the legally valid norms of a given system derive their validity from the same basic norm (Raz 1979, 127–129).