Just over 200 years ago Immanuel Kant suggested that "re-publican constitutions," a "commercial spirit" of international trade, and a federation of interdependent republics would provide the basis for perpetual peace. Our analyses for the years 1885–1992 indicate that Kant was substantially correct: democracy, economic interdependence, and involvement in international organizations reduce the incidence of militarized interstate disputes. The pacific benefits of the Kantian influences, especially of democracy and trade, were not confined to the cold war era but extend both forward from that era and back many decades.