There is no certain way of telling in advance if the day- dreams of a life dedicated to the pursuit of truth will carry a novice through the frustration of seeing experiments fail and of making the dismaying discovery that some of one’s favorite ideas are groundless.

People who write obscurely are either unskilled in writing or up to mischief. – Peter Medawar.

There is no such thing as a Scientific Mind. Scientists are people of very dissimilar temperaments doing different things in very different ways. 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. What sort of mind or temperament can all these people be supposed to have in common?

There is no quicker way for a scientist to bring discredit upon himself and on his profession than roundly to declare – particularly when no declaration of any kind is called for – that science knows or soon will know the answers to all questions worth asking, and that the questions that do not admit a scientific answer are in some way non-questions or pseudo-questions that only simpletons ask and only the gullible profess to be able to answer.

Considered in its entirety, psychoanalysis won’t do. It is an end product, moreover, like a dinosaur or a zeppelin; no better theory can ever be erected on its ruins, which will remain for ever one of the saddest and strangest of all landmarks in the history of twentieth century thought.

In choosing topics for research and departments to enlist in, a young scientist must beware of following fashion. It is one thing to fall into step with a great concerted movement of thought such as molecular genetics or cellular immunology, but quite another merely to fall in with prevailing fashion for, say, some new histochemical procedure or technical gimmick.

In no sense other than an utterly trivial one is reproduction the inverse of chemical disintegration. It is a misunderstanding of genetics to suppose that reproduction is only ‘intended’ to make facsimiles, for parasexual processes of genetical exchange are to be found in the simplest living things.

The bells which toll for mankind are – most of them, anyway – like the bells of Alpine cattle; they are attached to our own necks, and it must be our fault if they do not make a cheerful and harmonious sound.

The attempt to discover and promulgate the truth is nevertheless an obligation upon all scientists, one that must be persevered in no matter what the rebuffs – for otherwise what is the point in being a scientist?

Scientific reasoning is a kind of dialogue between the possible and the actual, between what might be and what is in fact the case.