I believe in intelligence, and I believe also that there are inherited differences in intellectual ability, but I do not believe that intelligence is a simple scalar endowment that can be quanitified by attaching a single figure to it—an I.Q. or the like.

It is a common failing-and one that I have myself suffered from-to fall in love with a hypothesis and to be unwilling to take no for an answer. A love affair with a pet hypothesis can waste years of precious time. There is very often no finally decisive yes, though quite often there can be a decisive no.

I do not propose to criticize the fatuous argument I have just outlined; here, to expound is to expose.

A scientist is no more a collector and classifier of facts than a historian is a man who complies and classifies a chronology of the dates of great battles and major discoveries.

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.

It is the great glory as well as the great threat of science that everything which is in principle possible can be done if the intention to do it is sufficiently resolute.

The art of research [is] the art of making difficult problems soluble by devising means of getting at them.