  A different sort of concern that arises for reductionist views (and perhaps naturalistic views as well) is that it may pose particular problems for positivism. Specifically, if law is a normative phenomenon that gives rise to legal obligations, one might worry that it is not possible to reduce legal facts (i.e., facts about what our legal obligations are) to a set of purely non-normative facts, e.g., social ones. One might think that this would impermissibly transgress the familiar (though not uncontroversial) is-ought gap. (For a discussion of this sort of worry about positivism, see Shapiro 2011, 47–49.)