Michael Steven Green’s lecture is a defense of legal monism: Discussing the positions of a number of current Anglophone philosophers of law, including Ronald Dworkin, Scott Shapiro, and Mark Greenberg, as well as the monism of Hans Kelsen, he argues that all laws that exist, have existed, or will exist are necessarily part of the same legal system. Resting on a concept of „rules of authorization“, he concludes that we cannot help but be committed to a monistic approach.