Fiero Sraffa's Production of Commodities by Means of Commodities has stimulated the writing of numerous articles and books, as economic theorists have tried to come to grips with the implications of this seminal work. It has led to the reconsideration of other approaches to economic theory, and the demonstration of the absence of a theoretical basis for 'any notion of capital as a measurable quantity independent of distribution and prices' (Sraffa, 1960, p. 38) was a critical element in the 'reswitching' arguments of the 1960s (Samuelson et al., 1966; Harcourt, 1972). Sraffa's subtitle for his book was 'Prelude to a critique of economic theory', with the theory referred to being the neoclassical or marginalist explanation of prices and distribution that was developed from the 1870s. Keynes's theory of employment, presented in The General Theory of Employment, Interest and Money (1936a), also represents a fundamental criticism of this neoclassical approach, 1 since he tries to establish that the equilibrium position in the economy is not one of full employment. Even though they both provide the basis for fund;1mental critiques of the neoclassical approach to economics, these works ofSraffa and Keynes focus on different questions. The former is concerned with the determination of relative prices, given technology and final output, and the latter with the factors determining output and employment. On the surface, the two appear to be, at least potentially, compatible, since Sraffa's work leaves open the question of the determination of the level of output (Roncaglia, 1978, p. xviii). It has also been argued (Garegnani, 1979a, p. 79) that the replacement of the marginalist elements in Keynes's analysis by Sraffa's explanation of relative prices will provide a much firmer basis for Keynes's critique of the view that the 'normal' level of employment in .a capitalist economy is one of full employment.