In this document, Keynes outlines the need for a "monetary theory of production" to address why economic crises have not been solved. [1] Most economic theories, such as those of Marshall and Pigou, treat the economy as a "real exchange economy" where money is neutral and does not affect real things. [2] However, Keynes argues that money plays its own role and is not neutral. [3] He is developing a monetary theory of production to supplement existing real-exchange theories and address booms and depressions peculiar to economies where money is not neutral.

1. “A Monetary Theory of Production” (1933)
John Maynard Keynes, The Collected Writings, Volume XIII, 408-411
Why the problem of crises has not been solved in economics is found in “monetary
theory of production” (408). Economic theory, such that of Marshall’s, assume that
“crises do not occur” (411).
Money in neoclassical economics is “neutral” it does not affect “real things” This is a
“real exchange economy” (Keynes’s words and italics). Here, there is no distinction
between “a barter economy and monetary economy.”
What we need is a “monetary theory of production,” where “money plays a part of its
own” (408).
Most treatises in economics are “real exchange economy.” An example is Marshall’s
Principles of Economics, where he is concerned with “relative exchange value.” Another
example is Pigou.
The theories do not square with the “real world.” For example, Keynes mentions “sticky”
money wages (410).
“I am saying that booms and depressions are phenomena peculiar to an economy
in which—in some significant sense which I am not attempting to define precisely
in this place—money is not neutral.
“Accordingly I believe that the next task is to work out in some detail a monetary
theory of production, to supplement the real-exchange theories which we already
possess. At any rate that is the task on which I am occupying myself, in some
confidence that I am wasting my time.” (411)