Fine and Saad-Filho are wrong to insist that an abstract category of production should be the starting point of Marxist value-theory in logical, temporal and causal terms. Marx, in Capital, begins with a repertoire of simpler categories and slowly constructs the complex category of capitalist production. It is vital that exploitation should be seen as one phase of a process of capital-in-motion, and due weight given to money, competition and realisation.