Philosophy of Law; Philosophy of Science; Legal Epistemology; Theory of Law; Legal Positivism; Law.

This thesis is a brief study on legal positivism, a branch of legal theory and philosophy that emerged approximately two hundred years ago. More specifically, the work discusses one of its central theses, which affirms that the existence of a law does not depend on its moral value but the occurrence of socially verifiable facts such as the presence of authority and the generalized obedience of the group (separability thesis). Once we met these requirements, a system would be recognized as legal even if morally objectionable. But this task, in turn, depends on a method that provides objective criteria for identifying and describing the law. From this arise at least two different methodological proposals within positivism, the naturalist and normativism. The analysis of these models and the type of legal knowledge we can obtain through them constitutes the core of this work. Therefore, it is composed of three chapters. The first offers a general approach to legal positivism through a counterpoint to the millenary Natural Law tradition and its thesis that the law is not a neutral phenomenon but depends on a moral basis to exist (morality thesis). The second chapter turns to the exam to the naturalist and normativism methodological variants, through the analysis of the works of its leading figures, respectively, John Austin and Hans Kelsen. Finally, the third chapter resumes the discussion about the difference assumed by a positivist epistemology between the functions of describing and evaluating the law through a synthesis of the contemporary debate between H.L.A. Hart and Ronald Dworkin in which this theme plays a central role.