It was John Maynard Keynes who once said that 

the ideas of economists and political philosophers, both when they are right and when they are wrong, are more 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 influence, are usually the slaves of some defunct economist.

In some quarters, including many of America’s most powerful think-tanks, that quote remains immensely influential; I lose count of the number of times I have heard it quoted by intellectuals, young and old, who have committed their lives to changing the world by changing the way it thinks.