Marx wants us to be properly impressed with this difficulty, for he takes himself to be the first person in the history of economic thought to have been able to solve it, and spends many pages exploring dead-end solutions. Finally he lets us into the secret. There must be, he says, a commodity which creates more value in its use than it cost. And, he tells us, there is a very special commodity just of this kind: labour power. Suppose I, Moneybags, the capitalist, hire a worker for a day, thus purchasing ‘a day’s labour power’. How much should it cost me? Now schooled, at least from the business pages, in elementary economic theory, you might start talk- ing about supply and demand; how skilled the job is; how scarce the talent needed to do it; and, perhaps, how unpleas- ant the task and so on. But for Marx all of this is superficial and the price of labour is ultimately determined in the same way as the price of any other commodity. That is, by the quantity of socially necessary labour power required for its production.