“In general, if a man says, for instance, that the earth is flat, I am quite willing that he should propagate his opinion as hard as he likes. He may, of course, be right but I do not think he is. In practice you will, I think, do better to assume that the earth is round, although, of course, you may be mistaken. Therefore, I do not think we should go in for complete skepticism, but for a doctrine of degrees of probability.”