This paper challenges the widely held view of Immanuel Kant as the father of modern democratic peace theory. First, relying on a little-known writing by Kant, his Vorschriften zum Ewigen Frieden (Prolegomena to Perpetual Peace), I show that the Prussian philosopher unequivocally thought of his pacific federation as including both representative republics and non-republics. Therefore, Kant did not radically depart from other Enlightenment proposals for a peaceful confederation of sovereign states. Second, through a careful analysis of Giuseppe Mazzini’s writings on international politics, I demonstrate that the Italian revolutionary envisioned the possibility of a separate peace among democracies much more clearly than Kant and also came close to formulating an explicit causal hypothesis. Mazzini believed that Europe’s newly emerging democracies would establish a collective defense pact to ensure their survival, which would then become progressively institutionalized, leading to growing inter-democratic trust and the elimination of the security dilemma among democracies.
