The stakes are immense, the task colossal, the time is short. But we may hope - we must hope - that man's own creation, man's own genius, will not destroy him.

God gave me the stubbornness of a mule and a fairly keen scent.

I must be willing to give up what I am in order to become what I will be.

God did not create evil. Just as darkness is the absence of light, evil is the absence of God.

Only the [Catholic] Church stood squarely across the path of Hitler’s campaign for suppressing truth. I never had any special interest in the Church before, but now I feel a great affection and admiration because the Church alone has had the courage and persistence to stand for intellectual truth and moral freedom. I am forced thus to confess that what I once despised I now praise unreservedly.

A theory is something nobody believes, except the person who made it. An experiment is something everybody believes, except the person who made it.

Certainly there are things worth believing. I believe in the brotherhood of man and the uniqueness of the individual. But if you ask me to prove what I believe, I can't. You know them to be true but you could spend a whole lifetime without being able to prove them. The mind can proceed only so far upon what it knows and can prove. There comes a point where the mind takes a leap—call it intuition or what you will—and comes out upon a higher plane of knowledge, but can never prove how it got there. All great discoveries have involved such a leap.