Among scientists are collectors, classifiers and compulsive tidiers-up; many are detectives by temperament and many are explorers, some are artists and others artisans. There are poet-scientists and philosopher-scientists and even a few mystics ... and most people who are in fact scientists could easily have been something else instead.

For a scientist must indeed be freely imaginative and yet skeptical, creative and yet a critic. There is a sense in which he must be free, but another in which his thought must be very preceisely regimented; there is poetry in science, but also a lot of bookkeeping.

If a scientist were to cut his ear off, no one would take it as evidence of a heightened sensibility.

If politics is the art of the possible, research is surely the art of the soluble. Both are immensely practical-minded affairs.

The human mind treats a new idea the way the body treats a strange protein; it rejects it.

I like to think that when Medawar and his colleagues showed that immunological tolerance could be produced experimentally the new immunology was born. This is a science which to me has far greater potentialities both for practical use in medicine and for the better understanding of living process than the classical immunochemistry which it is incorporating and superseding.