Marx explains returns to capital by his theory of surplus value. For Marx, surplus value arises from the exploitation of workers. Capitalists hire labor power, and the use value of labor power is the ability for the workers to labor under the direction of the capitalists. Suppose the produced commodities (which include the means of production) and labor power are both sold at their (labor) value. Surplus value is the difference between the value added by the workers and the value of their labor power.
I think this account of exploitation is intended by Marx to be descriptive. It is not, for Marx, the basis of a normative judgement of capitalism. I have previously documented that many scholars and activists, over more than a century, have shared my view. In this post, I note two more references putting forth a view consistent with mine.2.0 Allen Wood
Allen Wood (1972) argues that Marx did not condemn capitalism as unfair. Marx considered justice to be assessed from a juridical point of view. According to the theory of historical materialism, this point of view belongs to superstructure, as opposed to the base. Thus, it can be, at most, a partial and one-sided point of view. And Marx cannot accept criticisms of capitalism from this point of view. Wood notes that, in Marx's account of capitalism, workers are described as subservient to capitalists. Once capitalist leads to sufficient economic development, this subservience and other brutal characteristics of capitalism are unnecessary. For Wood, one does not need to develop a philosophically sophisticated theory of justice to condemn capitalism on this basis. So, he thinks, he has offered an internally consistent reading of Marx on justice.3.0 William Baumol
William Baumol (1983) also argues that Marx did not think capitalism was unfair. In this article, he notes that Marx did not take wages to trend towards a physical subsistence level. Marx argued against the Iron Law of Wages. Baumol objects, in general, to the widespread use of strawpersons among economists. Many economists assigns positions to their predecessors which they rejected, repetitively. In fact, these predecessors often argued the exact opposite of these strawpersons.References
- William J. Baumol (May 1983). Marx and the Iron Law of Wages, American Economic Review. V. 73, N. 2: pp. 303-308.
- Allen W. Wood (Spring 1972). The Marxian Critique of Justice, Philosophy and Public Affairs. V. 1, N. 3: pp. 244-282.