How do states and other international actors move from one level or type of cooperation (which might be the absence of cooperation) to stronger levels or types? While international cooperation sometimes occurs in “big bangs,” in which states jump suddenly from low to high levels of cooperation on an issue, cooperation typically advances incrementally through one, or sometimes several, way stations, such as non-binding declarations, vague undertakings and narrowly plurilateral agreements. These incremental processes can be understood in terms of movement along three important dimensions of cooperation: substantive content, participation and – of special importance for this volume – legalization. In this chapter we identify three alternative routes to cooperation – “pathways” – that correspond to these three dimensions and examine the circumstances under which particular strategies of gradual cooperation will be more effective and are therefore more likely to be chosen as pathways to cooperation.

Our general argument is that states often cannot move directly to a cooperative solution because of informational, bargaining and distribution problems that hamper collective action. We begin with one such problem: the uncertainties that actors commonly face regarding the nature of particular issues, the nature and capabilities of potential cooperators, and political reactions at home and abroad. The three stylized gradual processes we identify here have as their key features that they (i) allow states to limit their commitments at any point in time to the level of cooperation they find appropriate given their uncertainty, and (ii) provide states with opportunities to resolve these uncertainties and undertake greater (joint) cooperative commitments as they are ready to do so. Each pathway offers advantages for dealing with particular types of uncertainty.