“A subject interests me and holds my attention only so long as it presents me with difficulties, only so long as I am at odds with it and have, as it were, to struggle with it; but once I have mastered it I hurry on to something else, to a new subject; for my interest is not confined to any particular field or subject; it extends to everything human. This does not mean that I am an intellectual miser or egoist, who amasses knowledge for himself alone; by no means! What I do and think for myself, I must also think and do for others. But I feel the need of instructing others in a subject only so long as, while instructing others, I am also instructing myself.”

Lecture I, , R. Manheim, trans. (1967), p. 2 <br class="br"> Lectures on the Essence of Religion http://www.marxists.org/reference/archive/feuerbach/works/lectures/index.htm (1851)