 In addition to his work refining solution concepts in noncooperative game theory Nash also made important contributions to cooperative game theory, an approach to modeling strategic interactions that extends things by allowing for the possibility that agents can be constrained by binding agreements. Among other things, cooperative game theory provides a set of tools for analyzing questions related to coalition building, as well as problems that arise in contexts where agents can rely on external authorities to enforce agreements. Nash’s most important contribution here was to introduce two approaches to analyzing the bargaining problem. This problem has been important in contractarian approaches to justifying moral and political orders, a subject we’ll return to in  section 4.