From The Lessons of History by Will and Ariel Durant
P55: “In progressive societies the concentration [of wealth] may reach a point where the strength of number in the many poor rivals the strength of ability in the few rich; then the unstable equilibrium generates a critical situation, which history has diversely met by legislation redistributing wealth or by revolution distributing poverty. “
The book goes on to discuss examples of the former (Solon/Athens) and the latter (Roman Empire, French Revolution, etc)