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98 Piero Sraffarate of profits (the price of the factor of production capital) and the‘quantity of capital’ per worker no longer holds, as we shall see below.Secondly, the theory must provide some results in terms of delimitingthe scope of possible events. For instance, as we have seen earlierin Chapter 4, Sraffa’s analysis brings out the distinction between basicand non-basic products with a number of interesting implications.Conversely, general equilibrium analysis, notwithstanding certain veryrestrictive assumptions (such as the convexity of production sets), doesnot provide definite results: we can have multiple equilibria (which ruleout comparative static analysis), instability (which rules out the ‘invisiblehand of the market’ thesis, together with the possibility of indicatingthe direction of change whenever there is a change in endowments,preferences or technology) and even no univocal relationship betweenthe available quantity of individual original resources and their price(Montesano 1995). As a matter of fact, whenever the so-called ‘generalequilibrium models’ are employed to say something about specific featuresof the real world, new restrictions are introduced within the model(a one-commodity world, a single representative agent, and so on) inorder to obtain some definite results. 3Axiomatic general equilibrium analysis is in itself wholly abstract:apparent reference to reality is only provided by the names attributedto the mathematical entities considered (goods, prices and so on).However, a meaning can be attributed to such entities only in the contextof the specific rules of the game being considered in the model,in connection to the set of assumptions adopted. All too often, theaxiomatic nature of the analysis is used as a pretext to avoid enteringinto any discussion about the nature of the assumptions adopted andtheir relationship with the real world; but then, there is no justificationfor adopting a set of ‘real’ names (namely, terms referring to actual economicentities). Thus, in Debreu’s (1959) general equilibrium analysisthere is no reason not to speak of angels (or demons, or avatars) insteadof economic agents, and of souls to be saved or damned (to lower orhigher circles of hell or paradise depending on the evaluations of theangels themselves) instead of commodities.3This is, for instance, the common practice with the ‘new Keynesian’ models,which purport to prove results with a strong appeal to common sense, underuntenable simplifying assumptions. In this case it is the plausibility of the resultswhich subtly stimulates acceptance of the theory rather than the other wayround, as should be the case when the theory is used to enhance our understandingof the world, rather than as a display of personal ability on the part of thetheoretician.Critique of the Marginalist Approach 99Sraffa’s criticisms concern, in various ways, the main attempts atbuilding marginalist theories aiming at robust results in interpretationof the real-world economy. Such is the case of the Marshallian theoryof the firm and the industry, in the 1925, 1926 and 1930 articles; suchis the case of the Austrian theory, based on the average period of production,in Chapter 6 of the 1960 book; and, more generally, such isthe case for all theories interpreting ‘capital’ as a ‘factor of production’the demand for which is inversely related to its price (Chapter 12 of his1960 book). In the following sections of this chapter we shall brieflyillustrate the latter criticisms, the case of the Marshallian theory ofthe firm and the industry having been considered already (§§ 1.3–1.5).Viewed in its general outline, Sraffa’s point is that the marginalistrepresentation of the economy encounters difficulties because we areconfronted with a multi-commodity world in which ‘capital’ cannot beconceived, together with natural resources, as part of the given data ofthe problem.6.2 Critique of the Austrian theoryAs we have seen, Sraffa’s 1960 book provides not only a theory ofprices of production within the framework of the classical conceptionof the economic system but also the tools for a radical critique of thetraditional marginalist theory of value, aiming at its very foundations.In this respect we can focus our attention on two chapters: the sixth,on the average period of production, will be considered in this section,while the final, twelfth chapter, on the choice of techniques, will bediscussed in the next section.The concept of the average period of production was first proposedby Jevons (1879, Chapter 7), to be later taken up and developed withinAustrian marginalist theory, and in particular by Böhm-Bawerk (1889),as a measure of the capital intensity of production. 4 Capital is hereinterpreted as ‘waiting’, measured in terms of time, and more preciselyas the length of the average period of time between the employment of(direct and indirect) inputs of labour and the completion of the processof production.In order to compute the average period of production, each commodityinput in the production process is substituted by the labour4Cf. Böhm-Bawerk (1889). An attempt of the same sort was undertaken byWicksell (1893). Subsequently, however, Wicksell (1901) recognised the imperfectionsof his attempts.