A nice passage from the 1861-63 manuscripts highlighting subsumption and the perversion of social labour in the forms of money and capital:
“The social productive power which arises from cooperation is a free gift. The individual workers or rather labour capacities are paid, and paid as separate ones. Their cooperation, and the productive power which arises therefrom, is not paid for. The capitalist pays 360 workers; he does not pay for the cooperation of the 360 workers: for the exchange between capital and labour capacity takes place between capital and the individual labour capacity. It is determined by the exchange value of the latter, which is just as independent of the productive power this labour capacity attains under certain social combinations as it is of the fact that the time for which the worker works and can work is longer than the labour time required for his own reproduction.
Cooperation, which is a productive power of social labour, appears as a productive power of capital, not of labour. And this transposition takes place within capitalist production in respect of all the productive powers of social labour. This refers to real labour. Just as the general, abstractly social character [IV-147] of labour — i.e. the exchange value of the commodity — presents itself as money, and all the qualities the product possesses as the representation of this general labour present themselves as qualities of money, in the same way does the concrete social character of labour present itself as the character and quality of capital.” MECW 260-261
In fact: Once the worker enters into the actual labour process he is already incorporated qua labour capacity into capital, he no longer belongs to himself but to capital, and therefore the conditions under which he works are rather the conditions under which capital works. However, before he steps into the labour process he enters into contact with the capitalist as the individual owner or seller of a commodity; this commodity is his own labour capacity. He sells it as an isolated commodity. It becomes social once it has entered into the labour process. The metamorphosis his labour capacity undergoes thereby is something external to it, in which it does not participate; it is rather something which is done to it. The capitalist buys not one but many individual labour capacities at the same time, but he buys them all as isolated commodities, belonging to isolated, mutually independent commodity owners. Once they enter into the labour process, they are already incorporated into capital, and their own cooperation is therefore not a relation into which they put themselves; it is the capitalist who puts them into it. Nor is it a relation which belongs to them; instead, they now belong to it, and the relation itself appears as a relation of capital to them. It is not their reciprocal association, but rather a unity which rules over them, and of which the vehicle and director is capital itself. Their own association in labour — cooperation — is in fact a power alien to them; it is the power of capital which confronts the isolated workers. In so far as they have a relation to the capitalist as independent persons, as sellers, it is the relation of isolated, mutually independent workers, who stand in a relation to the capitalist but not to each other. Where they do stand in a relation to each other as functioning labour capacities, they are incorporated into capital, and this relation therefore confronts them as a relation of capital, not as their own relation. They find that they are agglomerated. The cooperation which arises from this agglomeration is for them just as much an effect of capital as the agglomeration itself. Their interconnection and their unity lies not in themselves but in capital, or, the social productive power of their labour arising therefrom is a productive power of capital. Just as the power of individual labour capacity not only to replace but to increase itself — surplus labour — appears as a capacity of capital, so does the social character of labour and the productive power which arises from that character. MECW 30 262,63