Let us clear from the ground the metaphysical or general principles upon which, from time to time, laissez-faire has been founded. It is not true that individuals possess a prescriptive "natural liberty" in their economic activities. There is no "compact" conferring perpetual rights on those who Have or on those who Acquire. The world is not so governed from above that private and social interest always coincide. It is not so managed here below that in practice they coincide. It is not a correct deduction from the Principle of Economics that enlightened self-interest always operates in the public interest. Nor is it true that self-interest generally is enlightened; more often individuals acting separately to promote their own ends are too ignorant or too weak to attain even those. Experience does not show that individuals, when they make up a social unit, are always less clear-sighted than when they act separately.
John Maynard Keynes, "The End of Laissez-Faire" (1926)