 In the late 1970s, there emerged a competitor for the systems approach and all other Humean attempts to say what it is to be a law. Led by Armstrong (1978, 1983, 1991, 1993), Dretske (1977), and Tooley (1977, 1987), the rival approach appeals to universals (i.e., certain kinds of properties and relations) to distinguish laws from nonlaws.