"At some stage early in every Marxist textbook of political economy it is stressed that “capital” is not a thing, but a social relation, and an antagonistic social relation at that. But frequently, after this proclamation is made, the accumulation of capital is substantively treated as the accumulation of things, of machinery, buildings, raw materials, and so forth that are usually grouped under the rubric “constant capital”. This is fundamentally incorrect from a Marxist point of view: capital accumulation must be understood as the reproduction of capitalist social relations on an ever-expanding scale through the conversion of surplus value into new constant and variable capital."