Man's chief difference from the brute lies in the exuberant excess of his subjective propensities. His preeminence over them lies simply and solely in the number and in the fantastic and unnecessary character of his wants, physical, moral, aesthetic and intellectual. Had his whole life not been a quest for the superfluous, he would never have established himself so inexpungeably in the necessary. And from the consciousness of this, he should draw the lesson that his wants are to be trusted, that even when their gratification seems furthest off, the uneasiness they occasion is still the best guide of his life, and will lead him tosses entirely beyond his present powers of reckoning. Prune down his extravagances, sober him, and you undo him.
—William James, The Will to Believe, p. -1