The most important question we must ask ourselves is, 'Are we being good ancestors?'

I look upon ourselves as partners in all of this, and that each of us contributes and does what he can do best. And so I see not a top rung and a bottom rung - I see all this horizontally - and I see this as part of a matrix. And I see every human being as having a purpose, a destiny, if you like - the destiny that exists in each of us - and find ways and means to provide such opportunities for everyone.

One of the greatest rewards for doing can be the chances it gives to do some more - even better.

When I worked on the polio vaccine, I had a theory. I guided each [experiment] by imagining myself in the phenomenon in which I was interested. The intuitive realm . . . the realm of the imagination guides my thinking.

When you inoculate children with a polio vaccine, you don't sleep well for two or three months.

There is a moment of conception and a moment of birth, but between them there is a long period of gestation.

When things get bad enough, then something happens to correct the course. And it's for that reason that I speak about evolution as an error-making and an error-correcting process. And if we can be ever so much better - ever so much slightly better - at error correcting than at error making, then we'll make it.