1. The Marx passage in question is not very well-drafted, at least in the
English translation. I don't read German, but I wonder whether there might
be some tiny changes in tone in translation. For example, it makes a big
difference whether one says the common element among the commodities "can
be no other than" labor time, or "is nothing other than" labor time.
2. It might be more useful to point the discussion of the "common
substance" type of argument at scientific rather than mathematical issues.
The paradigmatic case of this kind of reasoning is the physical concept of
mass, which I think Marx is invoking in this passage. Because we have an
operational way of equating two objects (that they balance in a scale) this
_suggests_, but does not prove, that they have some conserved substance in
common (mass). Now in fact physicists have never satisfactorily explained
mass, although the conservation of mass has been a fruitful theoretical
principle for them. This isn't true all the time. For example, some
physicists tried the same idea with heat, assuming that because one can
operationally equate two systems through the equality of their
temperatures, they must have the same amount of some conserved substance
(which some of them called "phlogiston".) This turned out to be wrong, when
thermodynamic analysis showed that heat was a form of energy, and linked to
the degree of disorganization (or entropy) of the system.
3. I agree with the point that what Marx's very brief remarks support is
the tentative identification of a substance common to the commodities,
which I would call "value". Whether this actually exists or not is like the
problem of phlogiston. Neoclassical economics, in my reading, explicitly
denies the reality of value as an independent substance, and argues that it
is like heat, just a result of aggregating price relations in the economic
system. What, if it exists, it arises from (labor time, for example) is yet
another question, and I agree with Gil that this paragraph of Marx's really
offers no coherent argument in favor of the link. When I've read this in
the past I've thought that Marx assumed the reader would be familiar with
the labor theory of value, and that the purpose of this brief remark is
merely to contextualize his discussion in terms of what the reader already
knew.
Duncan
Duncan K. Foley
Department of Economics
Graduate Faculty
New School University
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