In the controversies of party politics, which move at the intellectual level of a preparatory school, it is counted a score against a man if he can be shown ever to have altered his mind on extremely difficult questions in a rapidly changing world. In the less puerile realm of science and philosophy it is not considered disgraceful to learn as well as to live, and this kind of stone has no weight and is not worth throwing.

C. D. Broad, Examination of McTaggart’s Philosophy, Cambridge, 1938, vol. 2, p. lxxiii