Never at War: Why Democracies Will Not Fight One Another (review)

One of the most significant findings in international relations is that no two well-established democracies have ever gone to war with each other. Although statistical tests have persuaded most scholars that this interdemocratic peace is neither a chance occurrence nor the by-product of other phenomena—like economic wealth—no consensus yet exists on why peace has prevailed among democracies. In this book, Weart constructs a persuasive theory to explain why democracies do not go to war with one another and presents evidence that further confirms the pattern of democratic peace.

Weart contends that democracies remain at peace because they share a common political culture. He begins by differentiating republican from autocratic regimes, noting that whereas the former permit open competition for political office, the latter deny it. Among those allowed to vote, republican polities tolerate criticism of the government and settle disputes peacefully. Weart then distinguishes democratic republics from oligarchic republics, based on the inclusiveness of the republican regime. In a democracy, the government does not suppress any significant segment of the population, typically allowing two-thirds or more of adult males to vote. In an oligarchy, on the other hand, the government denies the vote to a large segment of the public, generally granting the franchise to less than one-third of adult males, because it fears that freedom for the disenfranchised group would threaten its hold on power. Borrowing from social psychology, Weart contends that those permitted to vote in each regime constitute in-groups that receive conciliatory treatment. Those denied the vote—for example, criminals in a democracy and the suppressed group in an oligarchy—constitute out-groups that are denied equal rights and sometimes treated violently.

To explain how these political cultures affect the foreign policies of republican states, Weart first argues that democracies regard fellow democracies, and oligarchies regard fellow oligarchies, as members of the in-group, while each regards the other type of republic and all non-republics as out-groups. For this reason, and because humans strive to maintain cognitive consistency, “leaders will tend to act toward foreign leaders in the same ways they act toward domestic political rivals (at least to the extent that they believe the foreigners resemble those rivals)” (78). In his empirical investigation, which covers the entire span of human history, Weart does not find a single case of war between two well-established democratic states. This finding provides powerful support for the universality of the interdemocratic peace and buttresses existing studies that focus primarily on the period since 1816. Weart also uncovers an interoligarchic peace; oligarchic republics have only rarely fought one another. Despite this peace among democracies and among oligarchies, democratic republics have fought oligarchies, in part because each type of regime has regarded the other as an out-group and thus has not adhered to republican practices of conflict resolution in its dealings with the other. To corroborate his explanation of the interdemocratic peace, Weart derives additional implications about how democracies should behave toward each other if shared political culture really is the factor that accounts for this peace. Weart finds that democracies form international confederations, which set policy for member states and settle conflicts peacefully, and that they are more willing to negotiate compromises to international disputes than are non-democracies.

Although the basic argument is compelling, Weart’s theory is inconsistent with a few of the quantitative studies about the belligerence of democracies that he cites. If his theory is correct that a democratic political culture permits democracies to apply their nonviolent norms of conflict resolution only to relations with fellow democracies, then we would expect that a democracy and a non-democracy would be no less likely to go to war than a pair of non-democracies. Yet, Weart cites a number of studies that find that a dyad comprised of a democracy and a non-democracy is less likely to be at war than a pair of...