Republican Constitution and Peace

In a republic, citizens who bear the costs of war — in blood, taxes, and suffering — have a vote in the decision to go to war. A despot, by contrast, suffers no personal cost and may make war for personal glory or dynastic advantage. Kant's argument is structural: when those who decide are also those who bear the consequences, the decision calculus changes. Not that citizens are purely self-interested, but that the connection of decision to consequence creates a rational bias toward caution.

Kant carefully distinguishes republic from democracy. A republic is characterised by the separation of executive and legislative powers; a direct democracy, in which the people exercise executive power collectively, can be just as despotic as a monarchy. The key republican principle is representative government under law, not majority rule as such.

Republican constitutionalism is not merely a prudential mechanism — it is a realisation of the rule of law, which Kant holds to be a requirement of practical reason. The argument for peace through republican constitutions is therefore not merely empirical but normative: justice requires legal institutions, and legal institutions, properly structured, tend toward peace.

The First Definitive Article for Perpetual Peace appears in Section Two of Kant's Perpetual Peace.