The intensity of a conviction that a hypothesis is true has no bearing on whether it is true or false. The importance of the strength of our conviction is only to provide a proportionately strong incentive to find out if the hypothesis will stand up to critical evaluation.

Scientists are entitled to be proud of their accomplishments, and what accomplishments can they call 'theirs' except the things they have done or thought of first? People who criticize scientists for wanting to enjoy the satisfaction of intellectual ownership are confusing possessiveness with pride of possession. Meanness, secretiveness and, sharp practice are as much despised by scientists as by other decent people in the world of ordinary everyday affairs; nor, in my experience, is generosity less common among them, or less highly esteemed.

The alternative to thinking in evolutionary terms is not to think at all.

The Phenomenon of Man stands square in the tradition of Naturphilosophie, a philosophical indoor pastime of German origin which does not seem even by accident (though there is a great deal of it) to have contributed anything of permanent value to the storehouse of human thought.

Psychoanalytic theory is the most stupendous intellectual confidence trick of the twentieth century and a terminal product as well-something akin to a dinosaur or zeppelin in the history of ideas, a vast structure of radically unsound design and with no posterity.

I once spoke to a human geneticist who declared that the notion of intelligence was quite meaningless, so I tried calling him unintelligent. He was annoyed, and it did not appease him when I went on to ask how he came to attach such a clear meaning to the notion of lack of intelligence. We never spoke again.

The fact that scientists do not consciously practice a formal methodology is very poor evidence that no such methodology exists. It could be said-has been said-that there is a distinctive methodology of science which scientists practice unwittingly, like the chap in Moliere who found that all his life, unknowingly, he had been speaking prose.