49 With regard to sources as tokens, we must bear in mind that even if we agree on the recognition rule and the types of sources, public servants may be divided on whether a concrete custom is part of commercial law, for example. Suppose no one doubts that custom is generally a type of source, but the question of whether the actual conditions necessary for the creation of a given custom have been intrusive. In any event, it appears to be a purely factual disagreement that does not affect positivist conception. 32 Despite the fact that not everything is always discussed and that differences of opinion can generally be considered marginal, these are sometimes key cases, and they seem to present opposing views that highlight different characteristics of the same phenomenon. We have seen that Dworkin views the law as an interpretive practice in which a purpose is assigned to practice and that what the practice requires depends on that objective. If officials disagree, what is implicitly discussed is what best justifies state coercion. This is why differences of opinion are understandable and inherent in legal practice. In Dworkin`s design, differences of opinion are therefore not problematic, but actually show that his theory correctly reconstructs the practice. However, they pose a threat to positivism. 54 Moreover, differences of opinion on the validity criteria are not frequent and can be plausibly declared as marginal cases in which judges have a margin of appreciation compatible with the convergence necessary for positivism. Moreover, if differences of opinion on the criteria were common within a community, we would have doubts as to whether it did have a legal system.41 We believe that this is a pathological practice that is not able to perform most of the functions that we usually relate to the law. On the other hand, differences of opinion on sources can be reconstructed, either as empirical disagreements or as disagreements on the validity criteria.42 In this paper, I present the problem of legal differences, originally raised by Ronald Dworkin against Hartian positivism. According to Dworkin, differences are pervasive because the law is an argumentative practice in which participants make normative arguments.
Positivists who argue that the law depends on the agreement of public servants find it difficult to understand the fact that lawyers often disagree. First, I would like to set out the main arguments of the debate. I will then go to different levels where the lawyers do not agree. Taking these levels into account, I have expressed a pluralistic response that shows that fundamental positivist principles are not affected by Dworkin`s challenge.