This book is a psychological study of human nature. It includes, it is true, a philosophical chapter and also one in which are set forth the practical consequences to religion of some of its conclusions. The book is to be judged as primarily a psychological study of the aspects of human nature more conspicuous in mystical religion. Contents: mysticism and religion; mystical ecstasy as produced by physical means; yoga system of mental concentration and religious mysticism; Christian mysticism; methods of Christian mysticism; moral development of the great mystics; great mystics, hysteria and neurasthenia; ecstasy, religious and otherwise; main characteristics of trance consciousness; sense of invisible presence and divine guidance; religion, science and philosophy; disappearance of the belief in a personal Superhuman cause and the welfare of humanity.