ABSTRACT
This chapter introduces concepts that are useful in characterizing the landscape of interplay between and among governance systems and identifies several types of interplay that resemble one another in some ways but that deserve separate treatment in an effort to understand this phenomenon. It starts from the observation that much of the interest in interactions between distinct regimes flows from a concern that such interactions may generate harmful consequences with regard to the effectiveness of one or more of the regimes involved. Horizontal interactions are those that take place at the same level of social organization from local or regional interactions on up to national interactions and international or global interactions. The evidence that has accumulated so far makes it clear that institutional interactions can produce positive or even synergistic results under some circumstances and that various approaches to interplay management can prove effective at least on a case-by-case basis.
