How European disagreement turned out to be a strength rather than a weakness

The ancient Mediterranean was a graveyard of political experiments.

Greek cities cycled through regimes with startling speed, moving from kingship to aristocracy to tyranny to democracy and back again, often within a century or two; Athenian democracy in its classical form lasted roughly 140 years, from the reforms of Ephialtes and Pericles in the mid‑5…