Keynes speaks

"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 principles 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 these. 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, from The End of Laissez-Faire
(from a posting on the Society for the History of Economics website by Sumitra Shah of York University, Toronto, Canada)