One would say that man had always the feeling that a mere infirmity of his mind separates him from the Future. He knows it to be there, living, actual, perfect, behind a kind of wall around which he has never ceased to turn since the first days of his coming on this earth. Or rather, he feels it within himself and known to a part of himself: only, that importunate and disquieting knowledge is unable to travel, through the too narrow channels of his senses, to his consciousness, which is the only place where knowledge acquires a name, a useful strength and, so to speak, the freedom of the human city. It is only by glimmers, by casual and passing infiltrations that future years of which he is full, of which the imperious realities surround him on every hand, penetrate to his brain. He marvels that an extraordinary accident should have closed almost hermetically to the Future that brain which plunges into it entirely, even as a sealed vessel plunges, without mixing with it, into the depths of a monstrous sea that overwhelms it, entreats it, teases it and caresses it with a thousand billows. At all times, man has tried to find crannies in that wall, to provoke infiltrations into that vessel, to pierce the partitions that separate his reason, which knows scarcely anything, from his instinct, which knows all, but cannot make use of its knowledge. It seems as though he must have succeeded more than once. There have been visionaries, prophets, sibyls, pythonesses, in whom a distemper, a spontaneously or artificially hypertrophied nervous system permitted unwonted communications to be established between consciousness and unconsciousness, between the life of the individual and that of the species, between man and his hidden god. They have left evidences of this capacity which are as irrefutable as any other historical evidence. On the other hand, as those strange interpreters, those great mysterious hysterics, along whose nerves thus circulated and mingled the Present and the Past, were rare, men discovered, or thought that they discovered, empirical processes to enable them almost mechanically to read the ever-present and irritating riddle of the Future. They flattered themselves that, in this manner, they could consult the unconscious knowledge of things and beasts. Thence came the interpretation of the flight of birds, of the entrails of victims, of the course of the stars, of fire, water, dreams and all the methods of divination that have been handed down to us by the authors of antiquity. III