All these men (= old politicians) have learnt from experience to believe what they already believed before they had experience, for most people learn nothing from experience, except confirmation of their prejudices. To learn anything genuinely from experience requires a kind of open-mindedness which is the essence of the scientific temper, though many men of science are somewhat lacking in it.
Source: "The lessons of experience" (In: Mortals and Others: Bertrand Russell's American Essays, 1931-1935, v.1 (1975))
More info.: https://russell-j.com/EXPERIEN.HTM