ABSTRACT
This chapter discusses of a famous numerical example provided by Garegnani. Bidard has criticized the example as not dealing with heterogeneous capital at all. The chapter turns to a brief critical account of a contribution by Sato, who argued that reswitching is unimportant because it can be ruled out by assumptions that in Sato's judgement are 'weak' in some sense. Then, it argues that Bidard's argument as to the absence of reswitching on what he calls 'differentiability hypothesis'. The chapter deals with a proposition by Bidard concerning the concept of the 'marginal productivity of capital'. It stresses in particular that the finding of equality between the rate of profits and the marginal productivity of capital, implies nothing what so ever as regards the determination of the level of the rate of profits. 'Marginal equalities' must not be mistaken for substantive explanations of economic phenomena, that is, they must not be taken for the 'genuine article', as Sraffa said.
