For people who have studied psychical matters, or who have read any books on the subject, it is unnecessary to explain what a 'sitting' is. Novices must be asked to refer to other writings--to small books, for instance, by Sir W. F. Barrett or Mr. J. Arthur Hill or Miss H. A. Dallas, which are easily accessible, or to my own previous book on this subject called _The Survival of Man_, which begins more at the beginning so far as my own experience is concerned. Of mediumship there are many grades, one of the simplest forms being the capacity to receive an impression or automatic writing, under peaceful conditions, in an ordinary state; but the whole subject is too large to be treated here. Suffice it to say that the kind of medium chiefly dealt with in this book is one who, by waiting quietly, goes more or less into a trance, and is then subject to what is called 'control'--speaking or writing in a manner quite different from the medium's own normal or customary manner, under the guidance of a separate intelligence technically known as 'a control,' which some think must be a secondary personality--which indeed certainly is a secondary personality of the medium, whatever that phrase may really signify--the transition being effected in most cases quite easily and naturally. In this secondary state, a degree of clairvoyance or lucidity is attained quite beyond the medium's normal consciousness, and facts are referred to which must be outside his or her normal knowledge. The control, or second personality which speaks during the trance, appears to be more closely in touch with what is popularly spoken of as 'the next world' than with customary human existence, and accordingly is able to get messages through from people deceased; transmitting them through the speech or writing of the medium, usually with some obscurity and misunderstanding, and with mannerisms belonging either to the medium or to the control. The amount of sophistication varies according to the quality of the medium, and to the state of the same medium at different times; it must be attributed in the best cases physiologically to the medium, intellectually to the control. The confusion is no greater than might be expected from a pair of operators, connected by a telephone of rather delicate and uncertain quality, who were engaged in transmitting messages between two stranger communicators, one of whom was anxious to get messages transmitted, though perhaps not very skilled in wording them, while the other was nearly silent and anxious not to give any information or assistance at all; being, indeed, more or less suspicious that the whole appearance of things was deceptive, and that his friend, the ostensible communicator, was not really there. Under such circumstances the effort of the distant communicator would be chiefly directed to sending such natural and appropriate messages as should gradually break down the inevitable scepticism of his friend.