Throughout modern history, a variety of perspectives on capitalism have evolved based on different schools of thought.
Adam Smith was one of the first influential writers on the topic, with his book The Wealth of Nations, which is generally considered to be the start of classical economics which emerged in the 18th century. To the contrary, Karl Marx considered capitalism to be a historically specific mode of production and considered capitalism a phase of economic development that would pass and be replaced by pure communism. In conjunction with his criticism of capitalism was Marx's belief that exploited labor would be the driving force behind a revolution to a socialist-style economy. For Marx, this cycle of the extraction of the surplus value by the owners of capital or the bourgeoisie becomes the basis of class struggle.
This argument is intertwined with Marx's version of the labor theory of value asserting that labor is the source of all value, and thus of profit. Max Weber considered market exchange, rather than production, as the defining feature of capitalism; capitalist enterprises, in contrast to their counterparts in prior modes of economic activity, was their rationalization of production, directed toward maximizing efficiency and productivity; a tendency leading to a sociological process of enveloping 'rationalization'. According to Weber, workers in pre-capitalist economic institutions understood work in terms of a personal relationship between master and journeyman in a guild, or between lord and peasant in a manor.