Barred from philosophy and bored by facts, he wanted to teach his students something not wholly useless. The number of students whose minds were of an order above the average was, in his experience, barely one in ten; the rest could not be much stimulated by any inducements a teacher could suggest. All were respectable, and in seven years of contact, Adams never had cause to complain of one; but nine minds in ten take polish passively, like a hard surface; only the tenth sensibly reacts.

The Education of Henry Adams (1907)