This has been an interesting thread. I appreciate that Steve Kates specifically brings in Say's law in the discussion. Keynes was responsible for a "revolution" in economic (at least macroeconomic) theory, even if  "Keynes' theory emerged as the unifying glue to what had been emerging as a policy consensus", as Roy Weintraub says in his last post. Krugman gives it the more modest designation of a "reformation." Whether one regards it as a positive development, as Kates seems to suggest, and with which I agree, the fact itself is important.


It was also mentioned by some that Keynes, Robinson and Kahn played an active role in keeping the Keynesian movement alive. (Of course, this does not take away from what the theory stands for.)   I came across this in Skidelsky's biography  [Vol. III] of Keynes. 


[Quote] By the spring of 1937 Britain's national government had presided over four years of strong private-sector-led economic recovery from depression... Keynes seemed more isolated than he had been at any time in the inter-war years — not altogether unlike Winston Churchill, whose warnings of a coming war went unheeded.  [But] After four years of recovery, the American economy went into a steep decline in the summer of 1937, and the British economy followed suit. The patient was not yet cured. The decisive push, though, came from two men. It was Hitler who forced Keynesian economics on to Neville Chamberlain's anti-Keynesian government; and it was Keynes himself who made sure that the rearmament programme would be understood as an experimental test of his employment theory. 

The author of the Keynesian Revolution became its impresario. For two years the cure for an invalid economy was propounded by the invalid at Tilton  [Keynes was sick]...Keynes did not give up the "management" of his Revolution. Illness made him no less combative. "It seems to me the work of a sick man," the far from sprightly Keynes commented after reading an attempted refutation of his theory by Arthur Pigou, his Cambridge colleague. Pigou, too, had heart trouble. "Why is there such obstinacy and wilfulness in error?" he asked about Gottfried Haberler's Prosperity and Depression, which he got Kahn to savage in the Economic Journal, which he edited. [close quote]


The discussion has made me aware of needing to be a little more circumspect in teaching my undergraduate students about the Keynesian 'revolution', which one does in any case by pointing out all the public works programs already in place and to which Keynesian theory provided the theoretical underpinning.  Well, the non-econ majors quickly forget all about it and the econ majors form their own judgments as they go forward.

Cheers,  Sumitra