To help differentiate between oligarchies and democracies, Weart requires the classification not to differ from how the people at the time viewed the differences, the oligarchic elite should live in constant fear of a rebellion, and a war should not have been prevented if everyone had the vote in democracies. For example, it was the Greeks who first created the concepts of democracy and oligarchy and who classified Athens as a democracy while Sparta was an oligarchy. There was no mention in the historical record of fears of a revolt by the slaves in Athens, but such fears were frequent in Sparta and the Confederate States.