Why Legal Conventionalism Fails

The term “legal conventionalism” covers a set of broadly discussed legal theories explaining the fact of law’s existence by reference to the “conventional rule of recognition”. Some of them are aspiring to be so-called “fully fledged theories of law” and explain the normativity of law by reference to the same fundamental, conventional fact. The article presents some recently discussed views (including the ideas of E. Lagerspetz, A. Marmor, S. Shapiro) alongside with counter-arguments showing why conventionalism fails. Eventually, the basic points of critique can be shaped in terms of the distinction between instrumental and substantial reason.