It is just at this point that a number of investigators of mental disorder decline to go any farther on the path of research. Up to this stage, they say, one is relying upon ascertained facts, for one has the warrant of the patient’s own memory for the data obtained. Further analysis of a mental phenomenon must inevitably involve appeal to unconscious factors. And, once one has called in the unconscious as a means of explanation, psychology becomes a mere “tumbling ground for whimsies.” Probably there are few people to whom this statement does not appear to express the universal verdict of common sense. That is precisely what it does. But it should be unnecessary to point out that common sense alone is not always the most reliable guide to the discovery of fact. Unaided common sense not only informed men for centuries that the sun moved round the earth, but told them so with such finality and conviction that extraordinarily unpleasant consequences ensued for those who did not believe in such an obvious fact. And the old belief, wholly false as it is, has still to be unlearnt by every child. In the same way, the ‘common sense’ point of view which we have described is not flawless. It assumes that a patient is able not only to surmount the great difficulties of translating his experiences and beliefs precisely into words—a difficult task even for the well-educated person—but also to account for and explain them truthfully. It may, however, be pointed out that, though this last-mentioned misleading assumption is widespread, it is by no means so universal or so tenacious in man as the “belief of his own senses” that the sun goes round the earth. In fact, quite apart from the teachings of modern psychology, we frequently find well-founded suspicions in the lay mind that a man is not always competent to give the basis of and reasons for his mental condition. This view is summed up in the famous advice to the future judge, “Give your decision, it will probably be right. But do not give your reasons, they will almost certainly be wrong.”[40] What ordinary man, unversed in the subtleties of theology or comparative religion, could give to an agnostic a satisfactory account of the reason why—being let us say, a Christian, and a Protestant Christian—he is a Primitive Methodist or an English Presbyterian? Let us complicate the matter further by supposing that this sect to which he now belongs is not that in which he was brought up by his family! Many of the factors which have contributed to his present religious beliefs may have been entirely forgotten now, recallable only with the greatest difficulty[41] and with the help of a second person skilful in such investigation.