“There are three ways of arriving at an opinion on any subject.
The first is to believe what one is told; the second is to disbelieve it; and the third is to examine the matter for oneself. The overwhelming majority of mankind practise the first method; of the remainder, the overwhelming majority practise the second; only an infinitesimal remnant practise the third.
To believe what one is told is the right method for most people in regard to most questions. I believe there is a place called Vladivostok because the atlas says so and because I have met apparently veracious people who assert that they have been there. But if I were engaged in making a survey of eastern Siberia for the Soviet Government, I should have to verify the existence of Vladivostok for myself. Believing what one is told is proper whenever there is a consensus except in matters on which one is a professional expert. In many of the most important questions there is a local but not a world-wide consensus.
To disbelieve what one is told is the method of the rebel and as a general practice has nothing to recommend it. Wisdom is not achieved by refusing to believe that 2 and 2 make 4, or that there is such a place as Vladivostok. When the authorities are unanimous, they are usually right; when they are not, the plain man does well to suspend judgement. A general habit of intellectual rebellion is more foolish than a general habit of intellectual acquiescence, and if it became common it would make civilisation impossible.
It is wise, however, to feel some degree of doubt, greater or less according to circumstances, as regards even universally accepted opinion. Few things seemed more firmly established than the Newtonian theory of gravitation, yet it turned out to need correction. The rational man, in such cases, acts upon the accepted opinion but is willing to give a hearing to anyone who advances serious reasons against it.
Rationality is shown not so much in what you believe as in how you believe it. You are rational if you believe it on evidence and as firmly as the evidence warrants and if, further, your belief leads you to act only in ways which are no obstacle to the discovery of error.
Freedom of opinion is important, since, without it, no generally received error can ever be corrected; therefore no belief should be so firmly held as to lead to persecution of those who reject it. But so long as freedom of opinion is safeguarded, all except professional experts have a better chance of being right if they accept than if they reject the prevalent opinion.”