SOCIAL FACTORS
Closely related to the economic causes of urbanization were broader social causes. The eleventh and twelfth centuries were an age of great outward and upward social mobility. The exodus of serfs, free peasants, and lesser nobility from the manors was part of a more general pulsation and expansion of life, a quickening of the tempo, a search for new opportunities.
These social factors were also causes, and not only effects, of what Robert Lopez has called "the commercial revolution" -- but what might also be called "the industrial revolution" -- of the eleventh and twelfth centuries. In Lopez's words, there was a "continuous creation of-359-
new opportunities... to climb from one class to another Apprentices became masters, successful craftsmen became entrepreneurs, new men made fortunes in commerce and money_lending... Expansion was also stimulated by constant immigration from the country... Entire villages gradually lost to nearby towns all their inhabitants, peasants and landowners." 3 Although in most of the cities of Europe social and economic as well as political power eventually became more and mo re highly concentrated in the hands of a relatively small group of wealthy merchants, the original conception of the city as a place of opportunity to move upward in the social_economic hierarchy had a lasting influence on its character. It is significant that in the northern European cities of the eleventh and twelfth centuries and thereafter, and in some of the Mediterranean cities as well, sl avery hardly existed, in contrast to the situation in the cities of ancient Greece and imperial Rome and in the European settlements before 1000.