No theory changes what it is a theory about; man remains what he has always been.

A person who has been punished is not less inclined to behave in a given way; at best, he learns how to avoid punishment.

We have not yet seen what man can make of man.

Great scientific contributions have been techniques.

A failure is not always a mistake, it may simply be the best one can do under the circumstances. The real mistake is to stop trying.

I did not direct my life. I didn't design it. I never made decisions. Things always came up and made them for me. That's what life is.