In gesprekken over de invloed van ideeën op de praktische politiek wordt vaak een beroemde uitspraak van John Maynard Keynes aangehaald. De Britse econoom schreef in The General Theory of Employment, Interest and Money, dat in 1935 verscheen: ‘Practical men, who believe themselves to be quite exempt from any intellectual influence, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back.’