Dear James C.W. Ahiakpor,

Which long run are *you* thinking about: the one where "time is the essence of the matter" or the one where "everyone correctly foresees the situation"?  Which long run do you think Keynes ascribes to the Quantity Theory?

It seems to me that the "_this_ long run" identified as a misleading guide is the one where everyone correctly foresees the situation: the long run where "the ocean is flat again." However, in the long run where time is the essence of the matter, changes in the money stock is likely to have an influence both on the velocity of money and on the real volume of transactions.

Keynes is reminding us that when it takes considerable time to reach the full-employment equilibrium described by the classical model, our plans may change. Tomorrow does come, but it is not the tomorrow anticipated by the classical model.  

I'm reminded of Veblen's observation:
--quote
There are certain saving clauses in common use .... Among them are these: "Given the state of the industrial arts"; "Other things remaining the same"; "In the long run"; "In the absence of disturbing causes." It has been the praiseworthy endeavor of the votaries of this established law and custom to hold fast the good old plan on a strategic line of interpretation resting on these provisos....

Now, ... the state of the industrial arts has at no time continued unchanged during the modern era; consequently other things have never remained the same; and in the long run the outcome has always been shaped by the disturbing causes. 
--end quote
(The Vested Interests and the Common Man, 1919)

Michael Nuwer