"I am not writing for those who do not believe that there is such a thing as clairvoyance, nor am I seeking to convince those who are in doubt about the matter... I am addressing myself to the better-instructed class who know that clairvoyance exists, and are sufficiently interested in the subject to be glad of information as to its methods and possibilities; and I would assure them that what I write is the result of much careful study and experiment."