As for the excellent little wretches who grow up in what they are taught, with never a scruple or a query, ... they signify nothing in the intellectual life of the race.

The mark of a civilized man is his willingness to re-examine his most cherished beliefs.

The ultimate good desired is better reached by free trade in ideas [and] the best test of truth is the power of the thought to get itself accepted in the competition of the market.

Be willing to commit yourself to a course, perhaps a long and hard one, without being able to foresee exactly where you will come out.

The minute a phrase, becomes current, it becomes an apology for not thinking accurately to the end of the sentence.

A great man represents a great ganglion in the nerves of society, or to vary the figure, a strategic point in the campaign of history, and part of his greatness consists in his being there.

Many ideas grow better when transplanted into another mind than in the one where they sprung up.