Another Metaphor: The “Man from the Moon”

Interestingly, Sraffa employed also another metaphor as a shorthand to describe the same thing: the “man from the moon.” The note in which he used it was composed presum­ably toward the end of the early period of his work, that is, in 1929 or 1930.

The significance of the equations is simply this: that if a man fell from the moon on the earth, and noted the amount of things consumed in each factory and the amount produced by each factory during a year, he could deduce at which values the commodities must be sold, if the rate of interest must be uniform and the process of production repeated. In short, the equations show that the conditions of exchange are entirely determined by the conditions of production. (Sraffa Papers, D3/12/7/87)

This note is interesting for several reasons. First, while it does not refer to a photograph, it contemplates on what an impartial observer, coming from another planet, would see on earth and what he could infer with regard to relative prices and the rate of interest. He would see physical quantities of things (inputs) being transformed into other things (outputs). A photograph would have the task to show these quantities. It would not show the rate of interest and relative prices: these would rather be the result of the impartial observer’s mental work, seeking to find a system of relative prices that support the distri­bution of the social surplus in terms of a uniform rate of interest across all productive activities. This condition is superimposed on what could be seen in a photograph and reflects particular social institutions or “rules of the game,” such as free competition. From this it follows that the photograph metaphor is of limited use only, because it is unable to capture the essence of the problem at hand: the observer’s projection of given social conditions onto a given physical scheme of production and establishing the impli­cations that follow from them (interest rate, prices).

Second, presumably in 1942 when Sraffa resumed his constructive work and reread his old notes, he added (in pencil) “Man from the Moon” and also put two straight lines along the passage in the margin. These additions evoke two remarks. First, characteriz­ing the situation under consideration with reference to the man from the moon echoes an event that took place in British Parliament on the occasion of a debate on agricul­tural distress on May 30, 1820. In the debate Ricardo is reported to have said that, “because he consulted the interests of the whole community, he would oppose the corn­laws” (1820, 49). A Mr. Brougham, the Member for Winchelsea, who supported the agriculturalists’ motion in favor of additional protective measures, qualified Ricardo’s argument as if it came from a man who “had dropped from another planet” and lived in an “Utopian world” (ibid., 56).⁷ The reference to the “man from the moon” may thus be seen as a metaphor designed to indicate the need to take a detached point of view, to see things as they are and not through the tinted glass of some particular interest group. What was badly needed was an objectivist perspective rooted in indubitable facts, such as the productive transformation of things, that is, commodities, and not a partisan out­look on matters.⁸

Third, and closely related to what has just been said, one has to stay away from existing explanations of income distribution and relative prices and make a fresh start. The man from the moon was by definition in the lucky position of being unaffected by received doctrines (marginalist theory or the labor theory of value) and could seek a new solution to an old problem. This solution, Sraffa implied, the man from the moon could easily find because of his unprejudiced point of view—he is in fact taken to see at a glance what some economists do not see at all and others see only vaguely, namely, that the rate of interest and relative prices follow from the given conditions of production. Economic theory may be a formidable tool that allows us to grasp aspects of a complex subject matter, but it may also mislead or bedazzle us.

The metaphor of the man from the moon can be seen as a development of the met­aphor of the photograph. In our interpretation both are steps in Sraffa’s search for a nonsubjectivist, objectivist explanation of relative prices and income distribution, which was at the heart of Sraffa’s research program. We have put forward ample evidence from Sraffa’s papers in support of this interpretation and refrain from repeating ourselves here. The interested reader is asked to consult Kurz and Salvadori (2004, 2005), Gehrke and Kurz (2006), Salvadori and Signorino (2007) and Kurz (2012). We rather reflect upon the issues at hand around an annotation in one of Sraffa’s book we have not men­tioned up until now that provides a welcome foil for our discussion.

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