"Supply creates its own demand" is a formulation of Say's law. The rejection of this doctrine is a central component of The General Theory of Employment, Interest and Money (1936) and a central tenet of Keynesian economics. See Principle of effective demand, which is an affirmative form of the negation of Say's law.
Keynes's rejection of Say's law has on the whole been accepted within mainstream economics since the 1940s and 1950s in the neoclassical synthesis, but debate continues between Keynesian economists and neoclassical economists (see saltwater and freshwater economics).
Keynes's interpretation is rejected by many economists as a misinterpretation or caricature of Say's law — see Say's law: Keynes vs. Say — and the advocacy of the phrase "supply creates its own demand" is today most associated with supply-side economics, which retorts that "Keynes turned Say on his head and instead stated that 'demand creates its own supply'".
The exact phrase "supply creates its own demand" does not appear to be found in the writings of classical economists;[1] similar sentiments, though different wordings, appear in the work of John Stuart Mill (1848), whom Keynes credits and quotes, and his father, James Mill (1808), whom Keynes does not. See for more detailed information Kates (1998) Say's Law and the Keynesian Revolution: How Macroeconomic Theory Lost its Way..[2]
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