There are two different causes for the breakdown of medieval society, one of which, is that the Nobles didn't trust each other and petty jealousies arose. The other is that Nobles were the only ones to own land. The new middle-class merchants, made wealthy by trade, now questioned the authority of the landholders. The freed serfs also moved to large cities to work in factories or to become involved in trade. Medieval life and the feudal system it had fostered began to break down.
