The dissertation aims to expose the Ronald Dworkin's thesis that has come to be known as interpretivism, according to which the law is an "interpretive practice". The main objective is to understand the methodological contribution that this thesis represents to the theoretical understanding of the law, and the argument it offers against merely descriptive theories of law. To locate the contribution of Dworkin's theory, the dissertation presents, first, the methodological innovations that arise in the seminal work of Herbert Hart, The Concept of Law. The key idea that starts being discussed is that of the internal point of view. It is considered an argument that Hart himself would have "planted the seeds" of Dworkin's interpretivism. Dworkin's theory is then presented as a theory that is initially concerned to understand the controversy in the practice of law. For that, it relies on the argument of theoretical disagreements and on the argument regarding the "semantic sting". These arguments reveal the political character of legal practice that was disregarded by analytical positivism due to its commitment to understand this practice only through the approach of the philosophy of language. Interpretivism is then contrasted to the challenge posed by a contemporary positivist theory, which agrees that the legal practice has normative character, but intends to defend descriptivism in theory. Finally, in response to this challenge, it is presented the latest formulation of interpretivism, bearing on recent Dworkin's books, Justice in Robes and Justice for Hedgehogs. In these works, two arguments that are key to the understanding of Dworkin's interpretive theory receive its final formulation: the argument about the controversial character of legal practice and the unavailability of criterial explanations, and the argument about the impossibility of "Archimedean" (external) theories. Following the adoption of interpretive theory as the most appropriate way of looking at legal practice, the study concludes in the form of a research agenda for the theory of law and to legal sociology.