If you ask somebody how he knows something, he may say, “I have it on good authority,” or, “I read it in a book,” or, “It is a matter of common knowledge,” or, “I learned it at school.”  Any of these replies means that he has accepted information from others, trusting in their knowledge, without verifying their statements or thinking the matter out for himself.  And the greater part of most men’s knowledge and beliefs is of this kind, taken without verification from their parents, teachers, acquaintances, books, newspapers.  When an English boy learns French, he takes the conjugations and the meanings of the words on the authority of his teacher or his grammar.  The fact that in a certain place, marked on the map, there is a populous city called Calcutta, is for most

[15] people a fact accepted on authority.  So is the existence of Napoleon or Julius Caesar.  Familiar astronomical facts are known only in the same way, except by those who have studied astronomy.  It is obvious that every one’s knowledge would be very limited indeed, if we were not justified in accepting facts on the authority of others.

But we are justified only under one condition.  The facts which we can safely accept must be capable of demonstration or verification.  The examples I have given belong to this class.  The boy can verify when he goes to France or is able to read a French book that the facts which he took on authority are true.  I am confronted every day with evidence which proves to me that, if I took the trouble, I could verify the existence of Calcutta for myself.  I cannot convince myself in this way of the existence of Napoleon, but if I have doubts about it, a simple process of reasoning shows me that there are hosts of facts which are incompatible with his non-existence.  I have no doubt that the earth is some 93 millions of miles distant from the sun, because all astronomers agree that it has been demonstrated, and their agreement is only explicable on the supposition that this has been demonstrated and that, if I took the trouble to work out the calculation, I should reach the same result.

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But all our mental furniture is not of this kind.  The thoughts of the average man consist not only of facts open to verification, but also of many beliefs and opinions which he has accepted on authority and cannot verify or prove.  Belief in the Trinity depends on the authority of the Church and is clearly of a different order from belief in the existence of Calcutta.  We cannot go behind the authority and verify or prove it.  If we accept it, we do so because we have such implicit faith in the authority that we credit its assertions though incapable of proof.