Mill, John Stuart (1873). Autobiography. Indianapolis, I.N.: Liberty Fund, 2006.

  There was one cardinal point in this training, of which I have already given some indication, and which, more than anything else, was the cause of whatever good it effected. Most boys or youths who have had much knowledge drilled into them, have their mental capacities not strengthened, but over-laid by it. They are crammed with mere facts, and with the opinions or phrases of other people, and these are accepted as a substitute for the power to form opinions of their own: and thus the sons of eminent fathers, who have spared no pains in their education, so often grow up mere parroters of what they have learnt, incapable of using their minds except in the furrows traced for them. Mine, however, was not an education of cram. My father never permitted anything which I learnt to degenerate into a mere exercise of memory. He strove to make the understanding not only go along with every step of the teaching, but, if possible, precede it. Anything which could be found out by thinking I never was told, until I had exhausted my efforts to find it out for myself. As far as I can trust my remembrance, I acquitted myself very lamely in this department; my recollection of such matters is almost wholly of failures, hardly ever of success. It is true the failures were often in things in which success in so early a stage of my progress, was almost impossible. I remember at some time in my thirteenth year, on my happening to use the word idea, he asked me what an idea was; and expressed some displeasure at my ineffectual efforts to define the word: I recollect also his indignation at my using the common expression that something was true in theory but required correction in practice; and how, after making me vainly strive to define the word theory, he explained its meaning, and showed the fallacy of the vulgar form of speech which I had used; leaving me fully persuaded that in being unable to give a correct definition of Theory, and in speaking of it as something which might be at variance with practice, I had shown unparalleled ignorance. In this he seems, and perhaps was, very unreasonable; but I think, only in being angry at my failure. A pupil from whom nothing is ever demanded which he cannot do, never does all he can.