My life is pretty well at peace, and the profession is more of an avocation. It's a calling, if you like, rather than a job. I do what I feel impelled to do, as an artist would.

I think of evolution as an error-making and error-correcting process, and we are constantly learning from experience.

My ambition was to bring to bear on medicine a chemical approach. I did that by chemical manipulation of viruses and chemical ways of thinking in biomedical research.

Life is an error-making and an error-correcting process.

There is no such thing as failure, there's just giving up too soon.

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.