From the beginning I could not believe that the “efficient market” hypothesis was dependent on a pure Brownian motion white noise or any truly random… - Paul Samuelson

I think Marshall was a great economist, but he was a potentially much greater economist than he actually was. It was not that he was lazy, but his health was not good, and he worked in miniature.

Dynamic process analysis also liberates economists from the necessity of having separate theories of the “turning-points” in addition to theories of cumulative upward and downward swings. Even a simple theory of inventory cycles, or acceleration-multipliers, can explain all four phases of an idealized cycle.
At its best, dynamic analysis can enrich our understanding of possibilities without leading to credulity in new, over-narrow, monistic dogmas concerning the cyclical process.

Yes, Keynes was a genius. Yes, some of his ideas were inchoate and would not have lent themselves usefully to diagramming and symbolic manipulation. Yes, by the time of the Radcliffe committee many of his British admirers were still frozen in the Model T version of his system. And yes, Keynes resented excessive simplifying of his paradigms.
Nevertheless, in science it is not the incoherent, inchoate and ineffable that has a cash value. If that were so, Goethe would be a greater scientist than either Einstein or Newton. What matters is the Kuhnian paradigm that people who are not geniuses can use. That which so many scholars independently agreed upon cannot be independent of the text that Keynes wrote down for them to read. What is remarkable is not the cogency of the case that Leijonhufvud manages to muster, which is rather flimsy, but rather how strong was the latent demand in the 1970s for a work to debunk Keynesianism. Harry Johnson put the same point in a different way.