Up to this point, Marx observes, we have only talked about those two parts of capital equivalent to the wages paid to the workers (necessary labour) and that equivalent to profit (surplus labour). But there are two other parts of capital: the material of labour, and the instrument of labour.

As far as the simple production process is concerned, labour presupposes the existence of an instrument which facilitates the work, and of a material in which it presents itself, which it forms. This form gives it its use value. This use value becomes exchange value through exchange, to the extent that it contains objectified labour.

More (pdf, 71 KB): The Chapter on Capital: Part 13: The Action of Living Labour in the Process of Production (pp. 354-364)