This problem was raised again recently by Maurice Clavel in a series of decisive and willfully incompetent questions--that is, questions addressed to Marxist economists by someone who doesn't quite understand how one can maintain human surplus value as the basis for capitalist production, while recognizing that machines too "work" or produce value, that they have always worked, and that they work more and more in proportion to man, who thus ceases to be a constituent part of the production process, in order to become adjacent to this process. [AO: 232]
[T]he importance of human surplus value remains decisive, even at the centre and in highly industrialized sectors. [AO: 233]