  In particular, reductionist views take it that illuminating the nature of law is a matter of explaining what the law is, and how it operates, in terms of more foundational facts. As a result, first-order theories of law succeed to the extent that they accomplish this in an explanatorily powerful way (Marmor 2013). The goal of a first-order theory, on this sort of view, is to offer a metaphysical reduction of law: that is, to show that the phenomenon of law is actually constituted by, and fully reducible to, some other more foundational type of phenomenon (in the way that chemistry could in principle be reduced to particle physics). Thus construed, positivism, for example, would seek to explain the nature of law by reducing facts about what the law is, how it functions and what it requires, to more foundational social facts—e.g., about people’s behavior, beliefs and dispositions. By providing a reduction of this kind, a theory like positivism purports to illuminate the phenomenon of law itself by breaking it down into its constituents and explaining how they together make up the complex social practice that is the law. (For more on metaphysical reduction in general, see  Schroeder 2007, 61–83; see also the entry on  scientific reduction.) 