> Does Keynes have a theory of value ?
I saw a similar question on PEN-L. Here's my take.
First off, if you have a chance, refer to my first comment on Mike Beggs' post:
http://mailman.lbo-talk.org/pipermail/lbo-talk/Week-of-Mon-20100712/009839.html
Keynes didn't need an explicit theory of value in either of the two senses indicated in that post and, as far as I know, he didn't make explicit any theory of value. Microeconomics (aka price theory) deals with the theory of value in the sense of understanding (relative) price changes, and (at least in the General Theory) Keynes was not interested in the subject. Theory of value in the sense of figuring out the underlying substance, the basis of commodity production and exchange, as far as I know, has only been the explicit business of (some, not all) Marxists. There are Marxists (and neo-Ricardians) who think that the struggle for socialism does not need a labor theory of value.
Similarly, Carrol doesn't think that overcoming in practice the reality of value, i.e. abolishing commodity production, requires our understanding all this stuff. We'll either abolish commodity production by chance or we won't. In other words, revolutionary practice does not need revolutionary theory. Theory -- which is not really instrumental to any purpose or need or goal, should -- just for the fun of it -- strive to fit reality, but reality does not need to fit theory. I used to paraphrase Trotsky and say that there's nothing more practical than a good theory, but I guess we should instead say that the purpose of theory is never practical, because then it would be like a toolbox, and the existence of toolboxes implies that we believe we can manipulate our environment. And that's an illusion, of course, our environment is not only impermeable to our attempts to manipulate it but also incomprehensible.
But I digress... There may be a few marginal non-Marxist thinkers interested in the question. Historians of economic thought -- who tend to be marginal in the economic profession -- may also be interested. But since the economists don't need an explicit theory of value to study price changes, then they tend to avoid the issue altogether. Some economists think that discussing an explicit theory of value is veering into "metaphysics."
Now, Keynes (in the General Theory, ch. 4) addressed the issue of how to measure economic activity. He discussed how complicated the measurement of prices and output were in the empirical practice, and then proposed the use of plain monetary units and, complementarily, "units of employment": hours of labor hired, averaged using wage rates as the weights of the different types of labor. However, this didn't really address the issues that a theory of value is supposed to address: (1) the fundamental social process that underlies commodity production and exchange and (2) the variables that make prices change (relative prices, as opposed to the general level of prices, which was indeed one of Keynes' concerns in the GT). So, as far as I know, Keynes did not make explicit his theory of value (in either sense).