It is far better for a man to go wrong in freedom than to go right in chains.

A man who speaks out honestly and fearlessly that which he knows, and that which he believes, will always enlist the good will and the respect, however much he may fail in winning the assent, of his fellow men.

Only one absolute certainty is possible to man, namely that at any given moment the feeling which he has exists.

The secret of genius is to carry the spirit of childhood into maturity.

[Scientists] have learned to respect nothing but evidence, and to believe that their highest duty lies in submitting to it however it may jar against their inclinations.

That mysterious independent variable of political calculation, Public Opinion.

Nothing great in science has ever been done by men, whatever their powers, in whom the divine afflatus of the truth-seeker was wanting.