Considerazioni sulla nozione di sostituibilità a partire dal “prodotto marginale netto” di Marshall

The paper looks at the reactions that Marshall’s highly controversial notion of a ‘marginal net product’ has elicited among neoclassical economists from the 1930s to the 1970s. The immediate purpose is to highlight the radically different responses that traditional neoclassical theory, on the one hand, and its neo-Walrasian reformulation, on the other, have given to the problem that seems to underlie Marshall’s notion, namely, the difficulty in grounding the notion of factor substitution on purely ‘empirical’ considerations. It is further suggested that not only the traditional position, based as it is on the notion of capital as a ‘single quantity’, cannot be accepted, but that the same applies, though for different reasons, to the neo-Walrasian position.