Ideally, a republican form of government is best suited to maintain peace.
When the powers of government are separated into three branches—legislative, executive, and judicial—and when the supreme authority, the legislative branch, is elected by the people, then only this popular assembly will have the power to declare war.
Of the three forms of the state, that of democracy is, properly speaking, necessarily a despotism, because it establishes an executive power in which “all” decide, for or even against one who does not agree; that is, “all” who are not quite all, decide, and this is a contradiction of the general will with itself and with freedom (p. According to Kant, governments are morally obligated to pursue peace.
Here he drew a parallel between the proper domestic functions of governments and their international responsibilities.
Among the latter would be: having to fight, having to pay the costs of war from their own resources, having painfully to repair the devastation war leaves behind, and, to fill up the measure of evils, load themselves with a heavy national debt that would embitter peace itself and that can never be liquidated on account of constant wars in the is the easiest thing in the world to decide upon, because war does not require of the ruler…the least sacrifice of the pleasures of his table, the chase, his country houses, his court functions, and the like.
He may, therefore, resolve on war as on a pleasure party for the most trivial reasons, and with perfect indifference leave the justification which decency requires to the diplomatic corps who are ever ready to provide it (p. Kant stressed that we should not confuse a republican form of government with democracy.
This condition will continue so long as there exists no international mechanism to adjudicate disagreements among states, so Kant called for a federation of states (one that would ideally include every state in the world) vested with the authority to resolve conflicts among sovereign states.
We should understand that Kant did not favor a world-state.
Like many classical liberals, for example, Kant invoked international free trade as a self-interested activity that, over time, will teach people the inestimable economic benefits of peaceful cooperation over war.
Nations are less likely to wage war against other nations if those nations are mutually dependent on each other for essential goods and services.