Contemporary positivism has taken a communitarian turn. Hart, in the Postscript to the Concept of Law, clarifies that the rule of recognition is a special sort of social practice: a convention. It is not clear whether Hart, here, means “convention” in the strict sense elaborated by David Lewis, or in some weaker sense. A number of contemporary positivists, including Jules Coleman (at one point), Andrei Marmor, and Gerald Postema, have argued that the rule of recognition is something like a Lewis-convention. Others have suggested that the rule of recognition is conventional in a weaker sense -- specifically, by figuring in a “shared cooperative activity” (SCA) among officials. Chris Kutz, Scott Shapiro, and Jules Coleman (more recently) have...