The ILC Study Group on Fragmentation of International Law asserted that the proliferation of special regimes poses a threat to the unity of the international legal system. Chapter 6 challenges this assumption. It builds on the distinction made in epistemology between knowledge-that and knowledge-how. The idea of a special regime as a community of practice makes it a system of knowledge-how. As such, it is compatible with all of the legal positivist’s, legal realist’s and legal idealist’s conceptions of an international legal system, which either see it as a system of knowledge-that or a combination of a system of knowledge-that and a system of knowledge-how. In the former case, in no way does the proliferation of special regimes affect the unity of the international legal system. In the latter case, the unity of the international legal system is indeed affected, but only in a positive sense, as it increases the efficacy of international law relative to the assumed legal ideal.