I see weeds and flowers. I think of it in those terms, and we have to discriminate and distinguish between the two, to recognize and encourage those … - Jonas Salk

We were told in one lecture that it was possible to immunize against diphtheria and tetanus by the use of chemically treated toxins, or toxoids. And the following lecture, we were told that for immunization against a virus disease, you have to experience the infection, and that you could not induce immunity with the so-called "killed" or inactivated, chemically treated virus preparation. Well, somehow, that struck me. What struck me was that both statements couldn't be true. And I asked why this was so, and the answer that was given was in a sense, 'Because.' There was no satisfactory answer.

Know what is the purpose of life that you are inclined to serve, that you are drawn to. Do what makes your heart leap rather than simply follow some style or fashion. Not everyone can or should be a scientist. Not everyone can or should be any one thing. People need to know what kind of purpose they can serve.

Nothing happens quite by chance. It's a question of accretion of information and experience … it's just chance that I happened to be here at this particular time when there was available and at my disposal the great experience of all the investigators who plodded along for a number of years.