Chiassoni explains that in the early 1960s Norberto Bobbio put forward a descriptive theory of legal positivism consisting of two main parts, namely, a definition of legal positivism, according to which there is no law but positive law (the exclusivity thesis) and an analysis of legal positivism that identifies three versions of legal positivism: legal positivism as an approach to the study of law (scientific positivism), legal positivism as a theory of positive law (theoretical positivism) and legal positivism as a doctrine of obedience to positive law qua law (ideological positivism). He explains that legal positivism as an approach to the study of law involves a commitment to a value-neutral study of positive law; that legal positivism as a theory of positive law encompasses (what he refers to as) narrow theoretical positivism as well as broad theoretical positivism; and that we may distinguish between three versions of legal positivism as a doctrine of obedience to positive law qua law, namely, an unconditional version, a moderate, conditional, relative version, and a very moderate, conditional, relative version, and that these versions differ in important ways.