Doyle, Michael. "Liberalism and World Politics". The American Political Science Review, Vol.80, No.4 (1986): 1151-1169.

Doyle, Michael. "Liberalism and World Politics". The American Political Science Review, Vol.80, No.4 (1986): 1151-1169.

• The claim that domestic political liberalism creates the conditions for peace is common with modern democracies and stems from a belief that allowing the population which carries the burdens of war to decide about conflicts will limit conflicts. By this logic, the expansion of liberal democracy will eventually lead to global peace (1151).
• Although the author recognizes the immense diversity of liberalism, the type of liberalism which creates a democratic peace is defined with reference to Joseph Schumpeter and his concept of pacific liberalism resting on the dual systems of capitalism and democracy (1152).
• Dr. Schumpeter argues that the main cause of war was objectless imperialism -- expansion for its own sake -- and that this was primarily driven by export monopolies, self-sustaining military adventurism, and warlike instincts (1152-1153).
• Capitalism and democracy work to counter all three primary causes of imperialist warfare according to Dr. Schumpeter. The economics of capitalism remove the monopolistic drive to forcibly dominate markets and allow the industry of the population to be expended in labour rather than warfare. Democracy also limits military domination and allows for more rational and self-interested decision-making against war (1153).
• As an example of the anti-imperialist effect that capitalist democracy has on states, Dr. Schumpeter notes than the most capitalist and democratic power, the USA, has been the least imperialist, showing so much restraint to only conquer half of Mexico in the Mexican-American War (1153).
• The track record of Dr. Schumpeter's prediction of capitalist and democratic peace is mixed at best, holding true during most of the Cold War but not in the era prior to the First World War (1153-1154). The primary points of divergence are that Dr. Schumpeter's theory does not account for non-economic reasons for warfare (1154).
• Machiavelli proposed an opposite idea of political liberalism, predicting that republics would actually be more imperialist and belligerent than other forms of government. He proposes that the factitious nature of the republic would safeguard the public interest and therefore republics would be belligerent because resources contribute to the public good (1154-1155).
• Rather than economic factors as the drivers of conflict, Machiavelli's analysis focuses on essentialist qualities of humanity, saying that the human love for power and domination would always drive conflict so the greater ability of republics to survive war made them more belligerent (1155).
• This argument addresses the key points of Dr. Schumpeter's theories of the effects of democracy, but -- for historical reasons -- does not address the effects of capitalism on reducing warfare (1155).
• Contemporary democracies take from both their pacific and imperialist legacies simultaneously. Pacific liberalism rules between liberal democracies and prevents various conflicts of interest between them from erupting in conflict (1155-1156). Conversely, liberal governments are belligerent towards non-democracies (1156).
• Liberal states often declare war on non-democracies, and face severe difficulties in interacting with non-democratic states. They view these states as sources of instability or untrustworthy partners (1157).
• Emmanuel Kant's theory of liberal internationalism is useful in understanding the dynamics which unlay the mixed system of contemporary liberal states acting as peacemakers and aggressors. Kant proposes that all liberal nations will form an alliance based on common values, which will gradual expand until the entire world is at peace. To join this liberal alliance, states must be republics, participate in a mutual non-aggression pact, and practice hospitality towards foreigners (1157-1158).
• Kant explains this development towards a democratic peace partly through the inherent caution with which popular republics approach warfare. This does not mean that wars cannot be fought, but that they can only be fought to serve popular causes, normally those which advance liberal ideologies (1160).
• The creation of a peace between democratic countries is fostered by the growth of universal customs and social principles which are fostered by liberal democracies. Common principles encourages trust between republics, which prevents war, as does free speech domestically and internationally (1161).
• The free trade and immigration which comes alongside the universal 'hospitality' of a pacific union further encourages peace between these states, because warfare would interrupt the ties of capitalism between them and invite unpopular economic sanctions (1161). Only all three conditions together can lead to a democratic peace (1162). 
• The representations of the state and humanity presented by Dr. Schumpeter, Machiavelli, and Kant are very different, but ultimately Kant's description of humans as rational but prone to sympathy for their kind. This perception of human nature allows for both the pacific and aggressive aspects of liberalism exhibited by democratic states (1162).
• The lack of respect for non-democracies common in liberal states stems from multiple sources, including a belief that unpopular governments are illegitimate and require 'saving', and a concern that non-democracies are automatically bellicose and thus pose an existential threat to democracies (1162). 
• If peace really is an ultimate goal, than liberal republics and capitalist democracies must do a better job understanding and appreciating the diversity of political and economic systems when making decisions and actively fight against impulses to distrust or despise all non-democracies (1163).