There are many versions of legal positivism; perhaps as many as there are legal positivists around. All the versions of legal positivism, however, subscribe to the so-called Separation Thesis. This thesis basically maintains that detenriining what the law is, does not necessarily, or conceptually, depend on moral or other evaluative considerations about what it ought to be in the relevant circumstances. Legal positivists differ, however, and quite substantially, over the appropriate interpretation of this thesis. The so-called ‘strong’, or ‘exclusive’ version of legal positivism maintains that moral considerations never determine the legal validity of norms. ‘Soft’ positivists, on the other hand, do maintain that there is a close relation between legal validity and morality, but they hold that this relation is, at best, a contingent matter; it does not derive from the nature of law or legal reasoning as such. Soft-positivists claim that moral considerations determine legal validity only in certain cases, namely, in those cases which follow from the rules of recognition that happen to prevail in a given legal system.