Life is an error-making and an error-correctin g process, and nature in marking man's papers will grade him for wisdom as measured both by survival and by the quality of life of those who survive.

Our greatest responsibility is to be good ancestors.

Evolution favors the survival of the wisest.

There is hope in dreams, imagination, and in the courage of those who wish to make those dreams a reality.

Reply when questioned on the safety of the polio vaccine he developed: It is safe, and you can't get safer than safe.

It is said to await certainty is to await eternity.

I do what I feel impelled to do, as an artist would. Scientists function in the same way. I see all these as creative activities, as all part of the process of discovery. Perhaps that's one of the characteristics of what I call the evolvers, any subset of the population who keep things moving in a positive, creative, constructive way, revealing the truth and beauty that exists in life and in nature.