From Kant’s plan for perpetual peace to Rawls’s proposal of a law of peoples, liberal projects for world order assume the homogeneity of states’ regimes as a determinant factor for bringing about peace and moral progress. Particularly, at the foundations of Rawlsian internationalism is the ‘fact’ of democratic peace, considered to be a sound and immutable feature of the international system. This article questions this oversimplified reading of Michael Doyle’s hypothesis about the apparent existence of a ‘separate peace’ among democratic states. It argues that liberal projects for global order should consider the ‘separate peace’ merely as a working hypothesis and they should address also the problematic aspects related to it, namely the unnecessary aggressiveness that democratic states show towards non-democracies and the coercive – and possibly illiberal – nature of the Society of Peoples.
