In accounting for phobias like these psychologists have, as a usual thing, fallen back on pure theory, and—especially when strongly influenced by the evolutionary doctrine—have been wont to attribute them to the emergence of ancestral traits and instincts once of real biological value. But recent investigation has made it certain that this ancestral revival theory is both superfluous and erroneous, and tends to hinder rather than help an understanding of the mechanism and consequences of fear. For one thing, there is the fact that agoraphobia and claustrophobia are not the only irrational fears. There may be a phobia for any conceivable act or object, and to explain all these in terms of the revival of ancestral instincts is surely beyond the power of the most vivid scientific imagination. Further than this, so far as abnormal fear of open or closed spaces is concerned, the researches of the medical specialists have rendered possible a satisfactory explanation—and an explanation that has much practical value—without harking back to the feelings and doings of primitive man. It has been found in every case scientifically studied that there is indeed a memory revival of past experiences, but that it is invariably a revival of experiences in the life of the victim himself, not of his remote ancestors. This is true of every kind of phobia. The sufferer may honestly declare his inability to recall any antecedent happening of a fear-inducing character. But it is found that, subconsciously at any rate, he always carries with him a vivid memory-image of some occurrence that at the time shocked him greatly; and that his phobia is due to the ceaseless presentation in his subconsciousness of this vivid memory-image. In proof of which may be cited the experiences of any medical man accustomed, in treating patients for nervous and mental troubles, to make use of modern methods—hypnotism, hynoidisation, and so forth—for exploring the obscurer workings of the human mind. Take, by way of illustration, a case of abnormal fear of open places successfully treated by Doctor Isador H. Coriat, a Boston neurologist of my acquaintance. The patient was a young man who for nearly two years had been tormented by an irrational fear of fields, parks, and public squares. His relatives and friends had argued with him, he had tried to conquer the phobia by force of will, but all to no purpose. Nor could he give any reason for his abnormal dread. Put into the hypnotic state, however, and questioned again, he recalled an incident that at once revealed its source. Two years previously, it appeared, he had been taking a horseback ride, when he unexpectedly galloped into an open field.