What does John Keynes mean by this quote from his General Theory? "The ideas of economists and political philosophers, both when they are right and when they are wrong ar emore powerful than is commonly understood. Indeed, the world is ruled by little else. Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually slaves of some defunct economist... I am sure that the power of vested interests is vastly exaggerated compared with the encroachment od ideas. Not, indeed, immediately, but after a certain interval..." (Keynes, The General Theory, p.383-384)