What is capital?
First, it’s not money.
Money can only perform money functions; buying and selling. But of course, there is a money circuit in the moments of capital circulation (it is only in the money form we can clearly aggregate between the original capital advanced and the surplus gained as measured in profit). The money form is the driving force of the acquisition of money power– a major incentive for capitalism. However, money power preexisted before the capitalist mode of production.
It is not commodities or things produced either. These as they are, are simple use values lying dormant– useless to capitalism if not put to market. As such, commodities must be put through the exchange circuit if the dead labor crystalized in them (surplus-value) will take on the money form and finally be realized as a greater capital than what was at the start of producing it (valorization).
Capital, furthermore, is not labor power as a commodity or commodity markets. Nor is it the production process. All these all are before capitalism, and each are a necessary for the capitalist mode of production.
Capital-ism is a social relation between capital and labor that permits the production of surplus-value.
And therein lies a world of contradiction.
Nature does not produce on the one side owners of money or commodities, and on the other men possessing nothing but their own labour-power. This relation has no natural basis, neither is its social basis one that is common to all historical periods. It is clearly the result of a past historical development, the product of many economic revolutions, of the extinction of a whole series of older forms of social production.
— Capital Vol. 1 Chapter 6
Words of David Harvey and added upon by Gospel Plow