The global commons—the oceans, the atmosphere, outer space—belong to all the world's people. So, ruling out war, the only way to govern their use is through international agreements… [W]hen considering a treaty, the questions we must ask ourselves are: do the costs outweigh the benefits? Does signing a treaty amount to a net loss or a net gain in terms of our national interests? Frank E. Loy, Under Secretary for Global Affairs, US Department of State (1999). 1
How do you know whether a treaty succeeds in improving on unilateralism? In the case of the Fur Seal Treaty you could look at the stock of fur seals both before and after the treaty came into force and see a difference like night and day. In most cases the data do not tell such a convincing story. One person could look at the Montreal Protocol and conclude that it had no effect. Another person could reach the opposite conclusion. 2
As indicated in Chapter 1 , to see more requires a structured imagination. It requires a theory of international cooperation. This chapter begins to lay down the foundation for such a theory.
Following on from Chapter 3 , I shall focus my attention in this chapter on public goods problems involving N countries (N can vary; the public good may be regional or global). In particular, I shall take the underlying game to be a prisoners' dilemma (PD). You will recall that these are the hardest situations for the international system to remedy. In other situations, countries will have strong incentives to supply a public good unilaterally. Alternatively, coordination will suffice to ensure that a public good is supplied—without the need for enforcement. 3 And in contrast to common property problems like the fur seal example, parties to a treaty seeking to supply a public good cannot gain by deterring entry. To the contrary, a key problem for international cooperation in the supply of public goods is how to broaden participation. This chapter focuses on the determinants of participation. Later chapters examine related aspects of the cooperation game.