Fire and Knowledge

All the fundamental functions of a healthy man ought emphatically to be performed with pleasure and for pleasure; they emphatically ought not to be performed with precaution or for precaution. A man ought to eat because he has a good appetite to satisfy, and emphatically not because he has a body to sustain. A man ought to take exercise not because he is too fat, but because he loves foils or horses or high mountains, and loves them for their own sake. And a man ought to marry because he has fallen in love, and emphatically not because the world requires to be populated.

—G.K. Chesterton, Heretics (1905), in The Collected Works of G.K. Chesterton, Volume I (1986), p. 76