Intuitions based on rational-choice theory help Downs and Jones to illumi complexity of reputational mechanisms. In particular, their analysis questions o ate the simplifying assumption that state actors are homogeneous, which was used for the sake of convenience in some earlier rational-choice models. But it also suggests the hypothesis that, contrary to speculation in much of the literature, reputational constraints will favor stronger rather than weaker actors The analysis of Downs and Jones indicates the value of articulating causal mechanisms. Rational-choice deductions that assume actor homogeneity are shown to be problematic-therefore, to the empirical investigator, probably not worth testing. One should get the causal mechanism right, in principle, before one sees whether it applies in the real world. The analysis that they offer suggests hypotheses about the segmentation of reputation and certain advantages of the strong that may have been insufficiently recognized. Several other causal mechanisms, suggested by rational-choice theory, are prominent in the literature, in this volume and elsewhere. Reciprocity in an impersonal and extensive environment such as that of world politics rests heavily on rational calculations of long-term mutual advantage. Signalling, cheap-talk and other means of screening good from bad types of players, may help to explain certain forms of rhetoric, ction, and institutions in world politics, including legalized talk, legalized forms of behavior,and legalized institutions, as Goldsmith and Posner explain in their paper. 6 Institutions, including legal institutions, may be invented in order to solve collective action problems by reducing transaction costs, providing information, and increasing the credibility of commitments. Legal institutions in particular may be valuable in dealing with problems of incomplete contracting. The menu of causal mechanisms identified by rational-choice theory is rich and tasty As we will see below, however, identifying mechanisms is not equivalent to successful explanation. It remains to theorize the conditions under which different mechanisms come into play. This is the really difficult task, which has not been solved. At present, we can more readily describe these mechanisms, and how they work, after the fact than we can specify the conditions under which one or more mechanism will operate. ex ante IS Robert O. Keohane, "Reciprocity in International Relations. "International Organization, volume 40, no. I(winter 1986): 1-27. 16 Goldsmith and Posner, this volume, pp 17 Keohane, After Hegemony, cited, chs. 5 and 6; Paul Milgrom, Robert North and Barry Weingast,"Th Role of Institutions in the Revival of Trade: the Medieval Law Merchant, Private Judges, and Champagne Fairs. Economics and Politics 1: 1-23. See also Frieder Roessler, Warren F. Schwartz and Alan O Sykes "The Economic Structure of Renegotiation and Dispute Resolution in the WTO/GATT System, "and Andrew Guzman and Beth A Simmons, "To Settle or Empanel? A Transaction Cost Approach to the WTO's Dispute Settlement Process, " both in this volume. ee abbott and Snidal. "Hard and Soft Law in International Governance. " "cited above. fn 5. and Roessler, Schwartz and Sykes, this volume.6 Intuitions based on rational-choice theory help Downs and Jones to illuminate the complexity of reputational mechanisms. In particular, their analysis questions the simplifying assumption that state actors are homogeneous, which was used for the sake of convenience in some earlier rational-choice models. But it also suggests the hypothesis that, contrary to speculation in much of the literature, reputational constraints will favor stronger rather than weaker actors. The analysis of Downs and Jones indicates the value of articulating causal mechanisms. Rational-choice deductions that assume actor homogeneity are shown to be problematic – therefore, to the empirical investigator, probably not worth testing. One should get the causal mechanism right, in principle, before one sees whether it applies in the real world. The analysis that they offer suggests hypotheses about the segmentation of reputation and certain advantages of the strong that may have been insufficiently recognized. Several other causal mechanisms, suggested by rational-choice theory, are prominent in the literature, in this volume and elsewhere. Reciprocity in an impersonal and extensive environment such as that of world politics rests heavily on rational calculations of long-term mutual advantage.15 Signalling, cheap-talk and other means of screening good from bad types of players, may help to explain certain forms of rhetoric, action, and institutions in world politics, including legalized talk, legalized forms of behavior, and legalized institutions, as Goldsmith and Posner explain in their paper.16 Institutions, including legal institutions, may be invented in order to solve collective action problems by reducing transaction costs, providing information, and increasing the credibility of commitments.17 Legal institutions in particular may be valuable in dealing with problems of incomplete contracting.18 The menu of causal mechanisms identified by rational-choice theory is rich and tasty. As we will see below, however, identifying mechanisms is not equivalent to successful explanation. It remains to theorize the conditions under which different mechanisms come into play. This is the really difficult task, which has not been solved. At present, we can more readily describe these mechanisms, and how they work, after the fact than we can specify the conditions under which one or more mechanism will operate, ex ante. 15 Robert O. Keohane, “Reciprocity in International Relations.” International Organization, volume 40, no. 1 (winter 1986): 1-27. 16 Goldsmith and Posner, this volume, pp. ---. 17 Keohane, After Hegemony, cited, chs. 5 and 6; Paul Milgrom, Robert North and Barry Weingast, “Th Role of Institutions in the Revival of Trade: the Medieval Law Merchant, Private Judges, and Champagne Fairs.” Economics and Politics 1: 1-23. See also Frieder Roessler, Warren F.Schwartz and Alan O.Sykes, “The Economic Structure of Renegotiation and Dispute Resolution in the WTO/GATT System,” and Andrew Guzman and Beth A. Simmons, “To Settle or Empanel? A Transaction Cost Approach to the WTO’s Dispute Settlement Process,” both in this volume. 18 See Abbott and Snidal, “Hard and Soft Law in International Governance,” cited above, fn. 5, and Roessler, Schwartz and Sykes, this volume.