Abstract

The hypothesis that democracies rarely fight each other is well-supported for the contemporary era. Yet evidence for it in another era of many democracies—Greece in the fifth century BCE—is weak at best. This article considers several reasons why the experience of the two eras may differ. It shows that the causal reasoning of the contemporary democratic peace depends on key assumptions about how institutions constrain leaders that did not apply well in ancient polities. Analysis of these differences helps to clarify theoretical understanding of interstate relations in both eras.