What is multilateralism? Multilateralism is the strategic propensity to rely on the actions of multiple participants rather than on the actions of a single state. Decision making is shared, presumably. Because the outcome is shaped by the decision inputs of multiple actors, the agreement may be more broadly acceptable to the international community, though the terms of the agreement are likely to be less demanding (since the terms are of a lowest common denominator sort) than for agreements resulting from more narrowly based participation.

According to John Ruggie, multilateralism consists of (i) the principle of collective security that an attack on one member of a coalition is an attack on all members (indivisibility); (ii) the principle that members are “equal before the law” and will be treated equally (nondiscrimination); and (iii) the principle that members take the long view rather than the short-term view, or that the average is more important than the marginal decision, or that they look at all the bargains on balance, not just separate bargains with each individual member (diffuse reciprocity) (Ruggie 1992). Lisa Martin observes that avoidance of large transaction costs in bargaining is an important explanation of why multilateralism is employed even by large states (Martin 1999). James Caporaso asks whether multilateralism is a means or an end (Caporaso 1993). Part of its complexity, perhaps, is that multilateralism is both a means and an end.