The actions of bad men produce only temporary evil, the actions of good men only temporary good ; and eventually the good and the evil altogether subside, are neutralized by subsequent generations, absorbed by the incessant movements of future ages. But the discoveries of great men never leave us; they are immortal; they contain those eternal truths which survive the shock of empires, outlive the struggles of rival creeds, and witness the decay of successive religions.

The clergy, with a few honorable exceptions, have in all modern countries been the avowed enemies of the diffusion of knowledge, the danger of which to their own profession they, by a certain instinct, seem always to have perceived.

He who knows most believes the least.

The great enemy of knowledge is not error, but inertness. All that we want is discussion; and then we are sure to do well, no matter what our blunders may be. One error conflicts with another, each destroys its opponent, and truth is evolved.

Sir, the slowness of genius is hard to bear, but the slowness of mediocrity is insufferable.

Men and women range themselves into three classes or orders of intelligence; you can tell the lowest class by their habit of always talking about persons; the next by the fact that their habit is always to converse about things; the highest by their preference for the discussion of ideas.

The duty of a philosopher is clear. He must take every pain to ascertain the truth; and, having arrived at a conclusion, he should noise it abroad far and wide, utterly regardless of what opinions he shocks.