Keynes, in his most famous observation, noted that we are ruled by ideas and by very little else. In the immediate sense, this is true. And he was right in attributing the importance to ideas as opposed to the simple influence of pecuniary vested interest. But the rule of ideas is only powerful in a world that does not change. Ideas are inherently conservative. They yield not to the attack of other ideas but, as I may note once more, to the massive onslaught of circumstance with which they cannot contend.
–The Affluent Society, 4th Edition, p. 17