The human faculties of perception, judgment, discriminative feeling, mental activity, and even moral preference, are exercised only in making a choice. He who does anything because it is the custom, makes no choice. He gains no practice either in discerning or in desiring what is best. The mental and moral, like the muscular powers, are improved only by being used . . . He who lets the world, or his own portion of it, choose his plan of life for him, has no need of any other faculty that the ape-like one of imitation. He who chooses his plan for himself, employs all his faculties.
 -John Stuart Mill, On Liberty 1859