There are savages without God in any proper sense of the word, but none without ghosts.

In matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable. That I take to be the agnostic faith, which if a man keep whole and undefiled, he shall not be ashamed to look the universe in the face, whatever the future may have in store for him.

Not only do I disbelieve in the need for compensation, but I believe that the seeking for rewards and punishments out of this lifeleads men to a ruinous ignorance of the fact that their inevitable rewards and punishments are here.

Action is the catalyst that creates accomplishments. It is the path that takes us from uncrafted hopes to realized dreams.

Friendship involves many things but, above all the power of going outside oneself and appreciating what is noble and loving in another.

The improver of natural knowledge absolutely refuses to acknowledge authority, as such. For him, skepticism is the highest of duties; blind faith the one unpardonable sin.

It sounds paradoxical to say the attainment of scientific truth has been effected, to a great extent, by the help of scientific errors.