Chapter Summary with Learning Objectives


The democratic peace refers to the theory that democratic states, for the most part, do not go to war with one another, making the spread of democracy desirable. It is supported by a good deal of evidence, but it also shows the different methodological issues involved in social science.

Recall that, as discussed in the introduction to Perspectives on International Relations, political science involves explaining something political by proposing several alternative hypotheses as to its causes, then testing those hypotheses against evidence using methodological approaches before coming to a conclusion. We must use our own judgment throughout this process; our knowledge of politics may be incomplete and biased, since we study human beings who are self-conscious and who can change their minds, and because we are often part of the politics or society we study. We must also use our sense of ethics, morality, and values; our conclusions can have a real impact on politics and society.

Statistical evidence shows that democracies do not, or only rarely, go to war with one another. But this empirical finding entails several social scientific issues. First of all, it depends on our sample size or the total number of cases we can study; relatively few democracies existed before World War II, so we only have enough cases to make an effective study after that point. Second, it depends on which cases we include, which in turn depends on our definitions of “democracy” and “war;” do new or weak democracies count as democracies, and do near-miss crises, small skirmishes, or militarized disputes count as war? Third, we can’t confuse correlation and causation; showing that democracy and peace often occur together does not explain why or how democracy causes peace (this is where our knowledge of causal arrows, perspectives, and levels of analysis helps us make alternative hypotheses or explanations). Fourth, we may have an overdetermined outcome – that is, a situation in which multiple causes interact in unclear, complex, and interrelated ways, leading to an outcome. Fifth, we may be unable to separate ourselves from our own biases – we likely come from backgrounds that make us think democracy is good. By using the tools discussed in this textbook – causal arrows, perspectives and levels of analysis, methodology, judgment, and ethics or morality – we can try to navigate these issues.

There are seven possible explanations for why democracy causes war. The identity perspective argues that democracies are more peaceful (an explanation at the domestic level of analysis) or that they share common domestic norms and institutions (at the systemic level). The liberal perspective argues that democracies have interdependent trade or that they belong to the same institutions, or that they are better at diplomacy, negotiation, and bargaining (all at the systemic level). Finally, the realist perspective argues that democracies belong to the same alliances or are better at using balance-of-power politics to avoid war (both at the systemic level). How we pick the best explanation and how we apply what we’ve found to the real world depends on the skills this textbook has taught you.

Learning Objectives

After reading this chapter students should be able to understand:

  • How different perspectives explain the democratic peace.
  • How methodological issues (sample size, definitions, correlation vs. causation, overdetermination, and bias) influence studies of the democratic peace.