"Tily (chapter 4) carefully documents how this Robertson version of 'Keynesian' economics succeeded in squeezing out Keynes' vision. The model behind Robertson’s vision is instantly recognisable by all students of economics today and consists of the idea that there exists a unique long-run equilibrium around which the economy fluctuates during booms and recessions... Apart from the fact that Keynes ... described rigidities as the classical explanation for unemployment, Tily makes it clear that this 'Keynesian' interpretation overlooks entirely that Keynes was concerned with the existence of multiple long-period equilibria in the General Theory. -- Colin Rogers, "Keynes vs the Keynesians: Keynes Rediscovered", History of Economics Review, Winter 2008.I have never quite understood the idea that Keynesian policy is about helping the economy reach equilibrium quicker. I thought The Arrow-Debreu model of intertemporal equilibria was the canonical neoclassical explanation of prices. That model doesn't allow for out-of-equilibrium behavior in real time. By now, it should be trivial to create models of multiple long-run equilibria. Keynes' explanation for multiple long-run equilibria, I think, had to do with long-run expectations - each state of expectations creates a different (set of?) long run equilibrium.
Ian Steedman reviews another volume in Hayek's collected works:
"Laurence White has been zealous in providing editorial footnotes to Hayek’s text and many of his notes are indeed helpful... Some footnotes seem to be quite unnecessary explications... The simple observation by Hayek, that the choice of production method may change in response to a relative input price change, is made the occasion of a long and irrelevant note on the 'economics of socialism' debate..., while an editorial reference to the 'reswitching controversy' cites a single discussion thereof – one by Leland Yeager! ... It might be felt here that Hayek’s text is being used for the promotion of ‘Austrian’ economics more generally." -- Ian Steedman on "F. A. Hayek. The Pure Theory of Capital. Volume 12 of the Collected Works of F. A. Hayek, History of Economics Review, Summer 2009.
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And not only does each state of expectations create its own long-term outcome, but there are multiple sets of long term expectations that create long term outcomes consistent with the expectations, there is no way a priori to know whether ones own state of expectations is necessarily among one of these "feasibly" expectations, and with neither change in one individual's expectations nor in the concrete facts, changes in other's expectations can swing an expectation back and forth between feasibly true and not feasibly true.
So the "long run" in the neoclassical sense is not the kind of thing that exists in the real world.
Robert; in traditional neoclassical theory long-run means equalization of the rate of profit across sectors and actual production = natural production. The economy is always moving in that direction, but in fact, it never reach it. In this contexts, keyensian policies may help.
But of course, Arrow-Debreu model is made of a very differente stuff.
Gualra
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