This force is a material force in the psychic class. If we confined our attention to blind senseless movements of one kind or another, in relation only with the volitions of the experimenters, and not capable of being explained by the mere imposition of their hands, we might see proof of the existence of a new unknown force, explicable as a transformation of nervous force, of organic electricity; and that would be much in itself. But the raps made in the table, or by the feet of it, are made in reply to questions asked. Since we know the table is only a piece of wood, when we ask it questions, we are really addressing some mental agent who hears and replies. It was in this class of phenomena that modern Spiritualism took its rise; namely, in the United States, in 1848, when the Fox sisters heard sounds in their chamber,--raps in the walls and in the furniture. Their father, after several months of vexatious investigation, finally had recourse to the traditional theory of ghosts, and, addressing his questions to the wall, demanded some kind of an explanation from the invisible _thing_ therein. This thing responded by conventional taps to the questions asked, and declared that it was the spirit of the former proprietor once assassinated in this his very home. The spirit asked for prayers and the burial of its body. (From this time on the replies were so arranged that one rap in response to a question signified _yes_, two meant _no_ while three meant an emphatic _yes_.) I hasten to remark at once that the tapped replies prove nothing, and could have been made unconsciously by the Fox sisters themselves, whom we can not consider to have been playing a little comedy since the raps produced by them in the walls astounded and overwhelmed them more, indeed, than they did any one else. The hypothesis of jugglery and mystification, dear to certain critics, has not the least application to this case, although I admit that rappings and movements are often produced as practical jokes by waggish persons. There is, of course, an unseen cause that originates these rappings. Is it within us or outside of us? Is it possible that we might be capable of doubling our personality in some way without knowing it, of acting by mental suggestion, of answering our own questions without suspecting it, of producing material results without being conscious of it? Or does there exist, around and about us, an intelligent medium or atmosphere, a kind of spiritual cosmos? Or, again, is it possible that we are surrounded by invisible non-human beings,--gnomes, spirits, and hobgoblins (there may be an unknown world about us)? Or, finally, is it possible that the spirits of the dead may survive, and wander to and fro, and hold communication with us? All these hypotheses present themselves to our minds, nor have we the scientific absolute right to reject any one of them.