Doubt everything at least once, even the sentence "Two times two is four."

Many a man who is willing to be shot for his belief in a miracle would have doubted, had he been present at the miracle itself.

To see every day how people get the name 'genius' just as the wood-lice in the cellar the name 'millipede'-not because they have that many feet, but because most people don't want to count to 14-this has had the result that I don't believe anyone any more without checking.

The feeling of health can only be gained by sickness.

If you are going to build something in the air it is always better to build castles than houses of cards.

With prophecies the commentator is often a more important man than the prophet.

Perhaps pure reason without heart would never have thought of God.