Unity of law is a two-level issue. It can – and should – be examined at the level of both particular instances of law and the plurality of those instances, that is, as internal and inter-instance unity. These levels interact, so that, for example, insights into the impact of the post-national condition on the internal unity of state legal regimes are relevant for a discussion of inter-instance unity too. The fracturing of the formal unity supposedly guaranteed by a Kelsenian or Hartian Master Rule also affects the way the unity of the plurality of law can be conceived of.