  Among the first analytic philosophers trained in law school, there was also a line of thought that departs from ordinary language and seeks to apply formal tools to studying the language of law. Especially noteworthy in this area is Alchourrón and Bulygin’s Normative Systems (1971), on the logic of norms and normative propositions. This work presents legal systems as deductive systems and aims to study the logical asymmetries between the processes of promulgation and the abolition of  laws.[10] Alchourrón was concerned with changes in the legal systems produced by the promulgation and abolition of laws, seeking to produce a formal system that would give substance to the legal bodies; the parallel with systems of belief induced him to focus on belief change, producing the first formal paper on the dynamics of belief (Alchourrón et al. 1985); the theory, known as AGM (by the initials of the last names of its creators: Carlos Alchourrón, Peter Gärdenfors and David Makinson), have had a major impact worldwide.