People were always asking for good sound proofs; doubt springs eternal in the human breast, even in countries where the Inquisition can read your very thoughts in your eyes.

In the present age doubt has become immune to faith and faith has dissociated itself from doubt.

A faith which does not doubt is a dead faith.

There lives more faith in honest doubt, Believe me, than in half the creeds.

Doubt is part of all religion. All the religious thinkers were doubters.

I am afraid I shall not find Him [God]: but I shall still look for Him, if He exists. He may be appreciative of my efforts.

O Lord, if there is a Lord, save my soul, if I have a soul.

Ten thousand difficulties do not make one doubt.

Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason, than that of blindfolded fear.

Wilt Thou not take the doubt of Thy children whom the time commands to try all things in the place of the unquestioning faith of earlier generations?

Do we, holding that the gods exist, deceive ourselves with unsubstantial dreams and lies, while random careless chance and change alone control the world?