Why does democracy matter? An investigation into the cooperative and constraining effects of democracy on third party joining in interstate war since 1816

This project tests various hypotheses about third party joining against the pattern of interventions in interstate wars over the 1816--1992 period. Drawing hypotheses from prominent explanations found within the 'democratic peace' literature, the dissertation undertakes a systematic evaluation of the various potential linkages between democracy and third party intervention. In addition to applying conventional democratic peace theories to the question of intervention, the project refines previous norms-based explanations for the 'democratic peace', offering an alternative account of the relationship between democracy and third party joining. This theoretical revision, based on a constructivist paradigm, links the conflict propensity of democratic states to the historical development of liberalism. The claim is that tensions between liberalism's central principles and the constitutive norm of sovereignty which underpins the modern international system help foster a sense of shared identity among the leaders of states with liberal constitutional systems.; The empirical work consists of an analysis of the pattern of third party joining between 1816--1992. Using logistic regression models, a large-N study tests the predictions generated from each of the contending 'democratic peace' theories. After establishing the plausibility of the various theoretical contenders by examining the aggregate behavior of states in the international system, a further investigation of three cases is conducted. These qualitative case studies examine the choices made by the leadership of three potential democratic interveners, the United States in World War I, Canada in Vietnam and Canada in the Persian Gulf War. The results of the case studies are used to refine the theoretical arguments consistent with the pattern of intervention observed in the large N-study.; The empirical findings, in both the statistical and case studies, reject one of the central claims of the conventional 'democratic peace' literature: that democratic leaders are constrained by the structure of their domestic institutions. Instead, the pattern of intervention seems most consistent with the predictions of norms based accounts of the democratic peace, suggesting that shared sense of identity impacts the intervention choices of democratic states to a greater extent than the structure of their domestic institutions.