The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.

The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.

William James used to preach the 'will to believe.' For my part, I should wish to preach the 'will to doubt' ... what is wanted is not the will to believe, but the wish to find out, which is the exact opposite.

I went to Russia a Communist; but contact with those who have no doubts has intensified a thousandfold my own doubts, not as to Communism in itself, but as to the wisdom of holding a creed so firmly that for its sake men are willing to inflict widespread misery.

There's a Bible on that shelf there. But I keep it next to Voltaire - poison and antidote.

Be isolated, be ignored, be attacked, be in doubt, be frightened, but do not be silenced.

Francis Bacon, a man who rose to eminence by betraying his friends, asserted, no doubt as one of the ripe lessons of experience, that ""knowledge is power