I conceive that the leading characteristic of the nineteenth century has been the rapid growth of the scientific spirit, the consequent application of scientific methods of investigation to all the problems with which the human mind is occupied, and the correlative rejection of traditional beliefs which have proved their incompetence to bear such investigation.

Agnosticism simply means that a man shall not say that he knows or believes that for which he has no grounds for professing to believe.

Life is too short to occupy oneself with the slaying of the slain more than once.

Natural knowledge, seeking to satisfy natural wants, has found the ideas which can alone still spiritual cravings. I say that natural knowledge, in desiring to ascertain the laws of comfort, has been driven to discover those of conduct, and to lay the foundations of a new morality.

I would rather be the offspring of two apes than be a man and afraid to face the truth.

For every man the world is as fresh as it was at the first day, and as full of untold novelties for him who has the eyes to see them.

Nothing can be more incorrect than the assumption one sometimes meets with, that physics has one method, chemistry another, and biology a third.