What Is Law and What Counts as Law? The Separation Thesis in Context

The separation thesis associated with the legal positivist tradition in legal philosophy holds that the legal validity of norms depends only on their sources, not on considerations of merit or value. In this essay I show that the separation thesis comes under pressure from cases in which an answer to the question: Is o an F? partly depends on the values associated with the nature of F. This is certainly the case when we try to determine whether an object is a work of art, for example. In response, proponents of the separation thesis would want to resist the analogy with art, and maintain that the ascription of legal validity to a norm does not involve any evaluative dimensions. I argue that this line of response is not very firm, and a better way to defend the separation thesis is to see it as an answer to the question of what makes it the case that an o counts as an F in the relevant society. I try to show that this latter type of question follows from the theoretical context in which the separation thesis comes up, namely, a reductionist explanation of legal validity. My purpose here is to show how a proper construal of the separation thesis, in the context of legal positivism’s reductionist ambition, goes a long way in supporting its truth.