It is accordingly fairly obvious that it is not of much use to take the trouble to expose the falsity of the pretensions of any isolated specimen of a douser or of a spirit medium. However that may be, some years ago, when I was staying in an ancient castle in the North of England, my hostess procured the attendance of a youth who had a great reputation as a douser, in order that I might test his pretensions. The youth arrived with his father, and had half a dozen Y-shaped hazel twigs ready for use. The party staying in the castle met him on the terrace, a broad gravel walk which surrounded the battlements. I asked him to walk round the castle and mark in our presence the spots at which his twig indicated the presence of subterranean water. The circuit was somewhat less than a quarter of a mile, and he indicated eleven spots. We placed obvious marks at each of these spots. I then took him into the castle and, aided by a friend, carefully blindfolded him with pads of cotton-wool over each orbit and a large silk handkerchief. We then led him out by a circuitous route on to the terrace and asked him to try again to indicate the spots which he had just discovered. He walked along as before and stopped at several spots, saying that his twig indicated water where he stood. He also made futile efforts by turning and throwing back his head, to catch a glimpse of some of the marks we had placed at the spots previously indicated by him. But the pads of cotton-wool effectually prevented him from seeing anything. In no case (as a large party of onlookers testified) were the spots indicated on his second circuit identical with, or even near to, those marked in the first circuit. His father said he was "upset" by the blindfolding. We then removed the bandage, and took him into a large courtyard beneath and across which from one corner to another a large subterranean conduit ran. We had arranged that the water should be running in abundance through this conduit. We told him that such a subterranean channel existed. He was left free and undisturbed, and his eyes were not bandaged. But he failed to discover the conduit altogether, although he crossed it several times; and he ended by declaring that his twig indicated subterranean water at a spot remote from the conduit, where some large vats stood for the purpose of storing rain-water! All this, of course, tended to prove the incompetence of the youth as a douser, and to make it probable that such successes as he had obtained elsewhere (and my hostess stated that they were very numerous and remarkable, and vouched for by members of her own family) were due to imposture.
But a single case like this does not bring one very far on the way to deciding the question as to whether there are persons who are genuinely and successfully guided to the discovery of subterranean water by strange sensations and by spasmodic movements of their limbs or of hazel-twigs held in the hands, due (as they declare) to an obscure influence which emanates from subterranean water and from buried metal. The fact is that we have in the belief in the guidance of the douser by occult influences a troublesome case of the fallacy in reasoning expressed by the words, "post hoc ergo propter hoc," or, to put it in English, "after this, therefore caused by this." Primitive man found that this mode of forming a conclusion very often led to a correct discovery of the connexion between two events, and he adopted it as a ready method of guidance, although it was frequently fallacious. It has taken ages, literally ages, to make people discard this mode of arriving at a conclusion in serious matters, and it is still usual in less vital affairs. To show that B followed upon the occurrence of A, even once, is, of course, a proper and useful way of forming a guess or a suggestion as to the cause of B, but still more is your guess legitimate if the sequence has occurred several times in your experience. But it is only a guess: a conclusion must not be accepted on that basis, although lazy and hasty people do adopt such conclusions. You must find out the details of the nature of A and also of B, and if possible how the one is connected with the other. And if you cannot do that you can still establish your conclusion and confirm your guess by showing that B invariably follows upon A, or that (in a long experience) only when A has been present, and never when A has not been present, has B occurred. If you cannot prove the truth of your guess by this experimental demonstration of the exclusion of other causes than A or by the experimental demonstration of the invariable occurrence of B after A has occurred, then you have to seek for evidence of a real connexion between A and B, though not an invariable one, by collecting a vast number of instances of the occurrence of B and finding out whether A has preceded it in such a large proportion of cases (as compared with those in which B has occurred without the previous occurrence of A) that the cases in which B follows A cannot be considered as accidental, but indicate a real causal relation of A to B.
This is always a difficult undertaking, whether we start with the guess that B is caused by A or that it is not caused by A. In the case of water-finding, water is found at depths of 30 feet to 100 feet and more below the surface by engineers without the aid of "dousers" every day, and this is so frequent and regular a proceeding that the percentage of cases in which dousers find water, that is to say in which B—the discovery of water—follows A (A being the employment of a supposed sensitive douser with or without his twig) does not—so far as I am able to judge without strict statistical evidence—exceed the percentage of successes in searching and digging for water by ordinary intelligent men without the introduction of A.
CHAPTER XL
BIRTH-MARKS AND TELEGONY
TWO widely-spread "beliefs"—in regard to the complicated and not generally familiar subject of the reproduction of animals—are, in addition to that dealt with in the last chapter, examples of the unjustified and primitive mode of forming a conclusion known as "post hoc ergo propter hoc." I refer, firstly, to the belief (which I have already mentioned) in the causation of what are called "birth-marks" by "maternal impressions," by which is meant the seeing of unusual and impressive things by the mother when with child; and, secondly, to the belief that a thoroughbred mare can be so affected or infected by the sire (say a zebra) of one foal as to convey to the foal of a later sire (say, a thoroughbred like herself) marks (such as stripes on the legs) which were not present in the second sire, though present in the first sire. This supposed occurrence is called "telegony," and is by some persons supposed to occur in dogs, cattle, and other animals, including man, as well as in the horse.
There is little support in ordinary experience for the belief that birth-marks are caused by maternal impressions, although some of those who are concerned in a professional way with breeding operations cling to it. In very ancient times we find that there was a belief in it, as shown by the story of the patriarch Jacob, who, wishing to obtain the birth of spotted or parti-coloured lambs from a herd of sheep, placed in front of the breeding ewes stakes or rods from which he had removed the bark in rings, so as to make them parti-coloured. He was supposed to have been successful in this way in impressing the visual sense of the maternal ewes with "parti-colouration," and the belief was that they in consequence produced dappled or parti-coloured lambs. The belief, though not general, is widespread among simple folk that such influences can and do act on animals, and it has been, and is by some, similarly held that a human mother may be influenced by surrounding objects, so that if her surroundings are beautiful she will produce a beautiful child. There is absolutely no ground for this belief—based upon experiment. It is merely an unreasoning assumption of "after this, therefore because of this," based upon the incomplete observation of a few accidental cases of vague coincidence and a tenacious clinging to the belief that it is so because it is difficult to prove that it is not so. No trustworthy investigation or experiment on the subject is on record.
But this unwarranted, untested belief, originating among barbarous peoples, has led further, owing to the inveterate love of marvels still common among us, to the notion (surviving to the present day) that the irregular coloured or obscure marks sometimes found on the skin of a child at birth, and vaguely resembling an animal or a fruit, or what not, are due to the mother having recently seen, under some sudden and startling circumstances, the object which the "birth-mark" on the child resembles. Thus we have the following stories related in a recent publication ("Sex Antagonism," by Walter Heape, F.R.S.). The author holds that this strange influence of "maternal impressions" is possible—a matter of comparatively small importance, since the real question is not as to the "possibility" but simply (as in a whole series of beliefs as to more or less improbable occurrences) whether there is or is not sufficient evidence that the connexion and influence believed in actually exists. Mr. Heape relates (without giving any detailed evidence whatever in support of the conclusion which he accepts) the supposed case of a red "mark" like a lizard found on a new-born child's breast being "produced" by the fall of a lizard from the ceiling (the event happened in China) on to its mother's breast shortly before the child's birth. Another case is that of a woman whose husband was brought home from work with his arm lacerated by machinery. Her child was born soon afterwards, and is stated to have had marks on one arm "similar to" those the mother saw on the corresponding arm of her husband. Another story is that of a lady who had a great craving for raspberries before her child was born, and accordingly bore a child with a red raspberry mark on its body!
In no case does Mr. Heape give any picture of the birth-mark and the thing supposed to be represented by it, nor state that he has seen either the mark or a picture of it. In no case is the statement of the mother as to her having been "influenced" as described in the narration, tested or examined in any way.