Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Doyle. 1983. Kant, liberal legacies, and foreign affairs. Philosophy and public affairs 12 (summer and fall): 205-35, 323-53.
PART I: WHAT IS LIBERALISM, AND WHY DON'T LIBERAL STATES FIGHT ONE ANOTHER
Liberalism entails three characteristics. Negative freedom (freedom from), positive freedom (opportunity/ability to use our negative freedoms), and representative government (to preserve the first two). Domestically, liberalism varies between conservative and liberal liberalisms. These differ in the emphasis they place on negative vs positive freedoms. Nevertheless, they both agree about four basic institutions. (1) Citizens are all equal and enjoy equal rights; (2) representative government; (3) private property rights; (4) economics governed by supply and demand.
Argues that there is such thing as a liberal peace. Realist arguments cannot account for it [he spends several pages outlining possible realist rebuttals and exposing their flaws]. Neither wealth, geography, or anything else does. There is a real statistical democratic peace.
Some liberal attempts to explain this liberal peace fall short. They explain why liberal states might be more pacific, but can't explain why they would still go to war with nonliberal states. This includes explanations about liberal norms, and about how citizens won't vote for war because [unlike monarchs] they have to bear the costs.
Kant, however, both explained and predicted a liberal peace (in 1795), based on three factors. (1) States must be republics; (2) they will gradually establish peace among themselves by expansion of a "pacific union"; (3) all states must respect a "cosmopolitan law" about how they treat foreigners in their midst.
There's some irony in Kant's theory. We form liberal democracies because they are best able to meet foreign threats [see also Olson 1993], yet liberal democracies tame aggression and selfishness in individuals, leading to global peace. That's why our violence pushes us toward peace whether we mean to or not.
There are three forces that push liberal regimes toward peace. (1) Citizens in a liberal state must personally bear the costs of going to war; (2) liberal republics respect other republics and expect to be respected by them; (3) the "spirit of commerce" and "cosmopolitan law" lead us to treat one another peaceably. Jointly these three conditions are sufficient for the establishment and expansion of a "pacific union" [not necessarily a formal or institutionalized union, just a set of states that won't fight]. An implication of these forces [particularly the second] is that liberal states expect other liberal states to be as just and accomodating as they are; they therefore are willing to negotiate with them. No such expectation exists in dealing with nonliberal states.
PART II: WHY LIBERALISM FAILS IN RELATIONS WITH OTHER STATES
Liberal states have all kinds of problems in dealing with other states. In dealing with strong illiberal states, we often miss opportunities for beneficial negotiations, exploiting divisions [say, between China and USSR], and so on, because we aren't engaging in pure realpolitik--instead, we are battling what the other side stands for [illiberalism and violation of human rights. In dealing with weak illiberal states, our supposedly liberal ends have often led to remarkably illiberal policy [imperialism in Africa, propping up dictators (even in place of elected leftists) during the cold war].
Liberal states also have a dismal record in helping the third world. Liberal liberals get mad at tyrants who abuse their subjects and want to cut off trade with them; conservative liberals get mad that we don't support such tyrants to defend liberalism globally. Refusing to deal with tyrants hurts our economy or security, depending on who you ask. Moreover, we are exceptionally bad at deciding whether and how to give of our excess in order to provide the "positive freedoms" of opportunity and development to the Third World.
The few successes we have had involve promoting human rights and encouraging free trade/investment with the Third World. Even there, the record isn't great.
"Resolving all these liberal dilemmas may not be possible without threatening liberal success" (344), because it would require putting pure realists at the head of the state (which would probably require an independent military bureaucracy or something else intolerable).
Doyle begins on 344 describing his (rather radical) prescriptions for implementing a more liberal foreign policy.
Research by the same authors
Research on similar subjects