Opposites and oppositions lead to confrontations along class lines, geographic lines, cultural lines, color lines, racial lines. The traditional confrontation of rural vs. urban life is doubly underlined by two factors: first, the countryside operates generally on a use economy with pay for services largely in kind or by barter. The city operates under a market economy with payment for services usually in money. Second, the standards of life and work are more primitive in the countryside than in the city. Third, as the civilization advances toward maturity, city population increases while it declines in the countryside. Consequently vigorous, energetic, adventurous people leave the deteriorating countryside. Increasingly the owners of land and capital live in the cities, visiting the countryside for holidays and recreation, leaving rural areas to servants, peons, serfs and slaves. Small owning farmers are bought out or expropriated. Unable to make a living in the countryside they move to the city. Lacking city skills they work as casual labor or are unemployed. The city is divided between enterprisers, their subordinates, owners of country estates and members of the state bureaucracy on one side and vassals, servants, serfs, and slaves and the unemployed on the other. The rich and powerful become richer and more powerful. The poor and dependent grow in numbers--protest, demonstrate, riot, revolt. This class struggle dominates public life in the urban centers of every civilization. The rich offer petty reforms and minor benefits to the impoverished, semi-employed city masses. At the same time the urban oligarchy breaks up into rival factions: the Ins and the Outs. The Ins hold public jobs, spend public money, award contracts and pass around favors. The Outs wait and maneuver for their turn at the public pie-counter. Both Ins and Outs appeal for mass support. Oppositions and confrontations lead to conflicts which have studded the life of every civilization. Conflicts include wars which may be divided into six groups: (1) Wars of expansion, conquest, colonization directed toward the enlargement of the territories included in the civilization. (2) Wars of survival among adjacent nations and empires. (3) Wars fought to suppress unrest and revolt in the colonies and dependencies of an empire or civilization. (4) Wars fought to repel the invasion of migrating peoples attempting to occupy territory over which an empire or a civilization claims jurisdiction. (5) Peasant, serf and slave revolts and rebellions against the authority of empires or civilizations. (6) Civil wars to determine the leadership of particular empires; wars of leadership succession; conflicts and power seizures within particular oligarchies.