Here’s something interesting from Axel Leijonhufvud. It’s a response to Luigi Pasinetti’s book on Keynes, but really it’s an assessment of the Keynesian revolution in general.
There really was a revolution, according to Pasinetti, and it can be dated precisely, to 1932. Leijonhufvud:
By the Spring of that year, Keynes had concluded that the Treatise could not be salvaged by a revised edition. He still gave his “Pure Theory of Money” lecture series which was largely based on it but members of his ‘Circus’ attended and gave him trouble. The summer of that year appears to have been a critical period. In the Fall, Keynes announced a new series of lectures with the title “The Monetary Theory of Production”. The new title signaled a break with his previous work and a break with tradition. From this point onward, Keynes felt himself to be doing work that was revolutionary in nature.
What was revolutionary about these lectures was that they weren’t about extending or modifying the established framework of economics, but about adopting a new starting point. A paradigm in economics can be thought of as defined by the minimal model — the model that (in Pasinetti’s words) “contains those analytical features, and only those features, which the theory cannot do without.” Or as I’ve suggested here, the minimal model is the benchmark of simplicity in terms of which Occam’s razor is applied.
For the orthodox economics of Keynes’s day (and ours), the minimal model was one of “real exchange” in which a given endowment of goods and a given set of preferences yielded a vector of relative prices. Money, production, time, etc. can then be introduced as extensions of this minimal model. In Keynes’ “monetary production” model, on the other hand, the “analytical features which the theory cannot do without” are a set of income flows generated in production, and a set of expenditure flows out of income. The minimal model does not include any prices or quantities. Nor does it necessarily include exchange — it’s natural to think of the income flows as consisting of profits and wages and the expenditure flows as consumption and investment, but they can just as naturally include taxes, interest payments, asset sales, and so on.
I don’t want to suggest that the monetary production paradigm has ever been as well-defined as the real exchange paradigm. One of Leijonhufvud’s main points is that there has never been a consensus on the content of the Keynesian revolution. There are many smart people who will tell you what “Keynes really meant.” With due respect (and I mean it) I’m not convinced by any of them. I don’t think anyone knows what Keynes really meant —including Keynes himself. The truth is, the Hicks-Patinkin-Samuelson version of Keynes is no bastard; its legitimate paternity is amply documented in the General Theory. Pasinetti quotes Joan Robinson: “There were moments when we had some trouble in getting Maynard to see what the point of his revolution really was.” Which doesn’t, of course, means that Hicks-Patinkin-Samuelson is the only legitimate Keynes — here even more than in most questions of theory, we have to tolerate ambiguity and cultivate the ability to hold more than one reading in mind at once.
One basic ambiguity is in that term, “monetary production.” Which of those words is the important one?
For Pasinetti, the critical divide is between Keynes’ theory of production and the orthodox theory of exchange. Pasinetti’s production-based Keynesianism
starts from the technological imperatives stemming from the division and specialization of labor. In this context, exchange is derivative, stemming from specialization in production. How it is institutionalized and organized is a matter that the minimal production paradigm leaves open (whereas the exchange paradigm necessarily starts by assuming at least private property and often also organized markets). Prices in the production paradigm are indices of technologically determined resource costs and, as such, leave open the question whether the system does or does not have a tendency towards the full utilization of scarce resources and, in particular, of labor. …
The exchange paradigm relies on individual self-interest, on consumer’s sovereignty, and on markets and private property as the principal institutions needed to bring about a socially desirable and harmonious outcome. In putting the division of labor and specialization at center stage, the pure production model, in contrast, highlights the “necessarily cooperative aspects of any organized society…
To an unsympathetic audience, I admit, this could come across as a bunch of commencement-speech pieties. For a rigorous statement of the pure production paradigm we need to turn to Sraffa. In Production of Commodities by Means of Commodities he starts from the pure engineering facts — the input-output matrices governing production at current levels using current technology. There’s nothing about prices, demand, distribution. His system “does not explain anything about the allocation of resources. Instead, the focus is altogether on finding a logical basis for objective measurement. It is a system for coherent, internally coherent macroeconomic accounting.”
In other words: We cannot reduce the heterogeneous material of productive activity to a single objective quantity of need-satisfaction. There is no such thing. Mengers, Jevons, Walras and their successors set off after the will-o-the-wisp of utility and, to coin a phrase, vanished into a swamp, never to be heard from by positive social science again.
The question then is, how can we consistently describe economic activity using only objective, observable data? (This was also the classical question.) Sraffa answers in terms of a “snapshot” of production at a given moment. Or as Sen puts it, in a perceptive essay, he is showing how one can do economics without the use of counterfactuals.
For Pasinetti, Keynes’ revolution and Sraffa’s anti-subjectivist revival of classical economics — his effort to ground economics in engineering data — were part of the same project, of throwing out subjectivism in favor of engineering. Leijonhufvud is not convinced. “Keynes was above all a monetary economist,” he notes, “and there are good reasons to believe” that it was monetary and not production that was the key term in the “theory of monetary production.” Keynes made no use of the theory of imperfect competition, despite its development by members of his inner circle (Richard Kahn and Joan Robinson). Or consider his famous reversal on wages — in the General Theory, he assumed they were equal to the marginal product of labor, which declined with the level of output. But after this claim was challenged Dunlop, Tarshis and others, he admitted there was no real evidence for it and good reason to think it was not true.  The fact that JMK didn’t think anything important in his theory hinged on how wages were set, at least suggests that production side of economy was not central to his project.
The important point for us is that there is one strand of Cambridge that rejects orthodoxy on the grounds that it misrepresents a system of production based on objective relationships between inputs and outputs, as a system of exchange based on subjective preferences. But this is not the only vantage point from which one can criticize the Walrasian system and it’s not clear it’s the one occupied by Keynes or by Keynesianism — whatever that may be.
The alternative standpoint is still monetary production, but with the stress on the first word rather than the second. Leijonhufvud doesn’t talk much about this here, since this is an essay about Pasinetti. But it’s evidently something along the lines of Mehrling’s “money view” or “finance view.”  It seems to me this view has three overlapping elements: 1. The atomic units of the economy are money flows (and commitments to future money flows), as opposed to prices and quantities. 2. Quantities are quantities of money; productive activity is not measurable except insofar as it involves money payments. 3. The active agents of the economy are seeking to maximize money income or wealth, not to end up with some preferred consumption basket. Beside Mehrling, I would include Minsky, Paul Davidson and Wynne Godley here, among others.
I’m not going to try to summarize this work here. Let me just say how I’m coming at this.
As I wrote in comments to an earlier post, what I want is to think more systematically about the relationship between the network of financial assets and liabilities recorded on balance sheets, on the one hand, and the concrete social activities of production and consumption, on the other. What we have now, it seems to me, is either a “real” view that collapses these two domains into one, with changes in ownership and debt commitments treated as if they were decisions about production and consumption; or else a “finance” view that treats balance-sheet transactions as a closed system. I think the finance view is more correct, in the sense that at least it sees half of the problem clearly. The “real” view is a hopeless muddle because it tries to treat the concrete social activity of production and consumption as if it were a set of fungible quantities like money, and to treat money commitments as if they were decisions about production and consumption. The strength of the finance view is that it recognizes the system of contingent money payments recorded on balance sheets as a distinct social activity, and not simply a reflection of the allocation of goods and services. To be clear: The purpose of recognizing finance as a distinct thing isn’t to study it in isolation, but rather to explore the specific ways in which it interacts with other kinds of social activity. This is the agenda that Fisher dynamics, disgorge the cash, functional finance and the other projects I’m working on are intended to contribute to.
 It’s a bit embarrassing that this “First Classical Postulate,” which Keynes himself said “is the portion of my book which most needs to be revised,” is the first positive claim in the book.
 Mehrling prefers to trace his intellectual lineage to the independent tradition of American monetary economics of Young, Hansen and Shaw. But I think the essential content is similar.