There may be things that are completely unknowable to us, so we must be careful not to treat the limits of our knowledge as sure guides to the limit of what there is.

I think that there are no forces on this planet more dangerous to us all than the fanaticisms of fundamentalism, of all the species: Protestantism, Catholicism, Judaism, Islam, Hinduism, and Buddhism, as well as countless smaller infections. Is there a conflict between science and religion here? There most certainly is.

We need to let our children grow up to face the world armed with knowledge, with much more knowledge than we ourselves had at their age. It is scary, but the alternative is worse.

Problems in science are sometimes made easier by adding complications.

What you can imagine depends on what you know. Philosophers who know only philosophy consign themselves to a janitorial role in the great enterprises of exploration that are illuminating the mysteries of our lives.

The way evolution always discovers reasons is by retroactive endorsement.

My faith in the expertise of physicists like Richard Feynman, for instance, permits me to endorse—and, if it comes to it, bet heavily on the truth of—a proposition that I don't understand. So far, my faith is not unlike religious faith, but I am not in the slightest bit motivated to go to my death rather than recant the formulas of physics. Watch: E doesn't equal mc2, it doesn't, it doesn't! I was lying, so there!