My thoughts on the question Iren posed in her notes below, i.e. "If circulation is socially necessary, a necessary condition for capital’s reproduction, on what grounds does Marx argue that it does not create value? Can his argument about specificity of use-value of commodity labour power be such a criterion? What is the difference between being socially necessary and value positing? Is his argument convincing?" (And at the last meeting we spent most of time on this issue.)
To rephrase the question, why does Marx treat production and circulation asymmetrically, i.e. one adds value while the other doesn't, when he admits that both are necessary for the reproduction of the economy?
I think we already know that Marx is implying 'necessary' in a different sense for production and circulation. As for production, it is necessary in the sense that it creates value through affecting use value; as for circulation, it is necessary in that it changes form of value, or realizes value already produced in production.
(Footnote: When Marx contrasts production and circulation, I think he is referring to circulation in a restricted sense of the word in that it involves only formal changes of value between money and commodity without affecting use-value at all. Thus when I say circulation I mean pure circulation as buying and selling excluding storage and transportation which, as Marx writes, are part of the production process disguised in circulation process, and therefore do add value.)
So, as Marx argues in Volume 2 of Capital, workers employed in circulation process is necessary and at the same time unproductive.
Marx has an interesting analogy in Volume 2:
Labour employed in the circulation process "behaves somewhat like the 'work of combustion' involved in setting light to a material that is used to produce heat. This work does not itself produce any heat, although it is a necessary moment of the combustion process." (208)
Now if our question is one of more fundamental type, i.e. "but still, why production, not circulation, as a site where labour is productive?" then I think the fact that value and use-value constitute dual nature of commodity, that thus there is no value creation without adding or conserving (in case of storage and transportation) use-value, and that (pure) circulation does not add or conserve use-value is enough to ground Marx's argument.