“Political liberalism was formulated in England by John Locke as the platform of the Glorious Revolution (1688), emphasizing among other things the primacy of individual freedom, government constrained by law and consent, and the rule of law in general. Economic Liberalism was added almost a century later by Adam Smith, stressing the benefits of the free market and the harms of state protectionism and colonial conquest.
“Expressing these and other Enlightenment ideas in the wake of the American and French revolutions, Thomas Paine (rather neglected in this context) and Immanuel Kant extended the liberal vision to the international arena. In his Perpetual Peace (1795), Kant suggested that the spread of republican regimes, incorporating representative government, separation of powers, and individual rights guaranteed by law, would act against the occurrence of wars. …
“In common with other liberals, Kant had not posited a general and equal right to vote and be elected. Indeed, similar to other liberals, he (although not Paine) had been apprehensive of democracy, which in classical times had been believed to have exhibited a tendency to degenerate into a rule of the mob incited by demagogues. Liberals had widely feared that democracy would turn into a tyranny of the majority and thereby threaten liberal rights.
“By the First World War, however, the franchise had steadily expanded in liberal countries so as to become practically universal in them or on the way to becoming so. A new compound, liberal democracy, had come into being, which Wilson believed was inherently peace desiring and consequently contributed to world peace as it proliferated and replaced war-like autocracies and oligarchies.”
Gat, Azar, “War in Human Civilization,” Oxford University Press (2006), pp. 570-71.