Complete understanding of any plane of Nature cannot DC gained from the level of that plane. No fish, even if endowed with sufficient intelligence, could study the element of water, for the simple reason that it cannot exist and function outside of water. The emotional plane can only be studied accurately from the level of the mental plane. The Student must gain a measure of self-consciousness in his mental body, and learn to use his mental means of cognition. Then he may investigate the planes below with complete understanding, without being deceived by their ever-changing phenomena and mistaking a passing temporary condition for a permanent characteristic. The ideal level for all occult investigation of and work in the three lower worlds of form is that of the causal body. Deceit and error are impossible to the student whose consciousness is free at that level. A description of causal consciousness is attempted in Chapter V of this volume. Hitherto research in this direction has remained largely in the hands of members of the spiritualist body, who have published a large number of books recording their findings upon the subject. While acknowledging the splendid contribution which has been made to human knowledge upon this subject by spiritualist investigators, writers and teachers, and by the various societies for psychical research, it must be slated that the student of occultism does not find himself convinced by them or able to regard their methods favourably. Firsthand experience and direct personal observation alone satisfy him, and of all the writings on the subject he tends to regard the literature of the Theosophical Society as most convincing, for in this field many authors claim to write from personal experience. The serious student of occultism approaches the question of the life after death in a strictly scientific attitude of mind. He knows that no demonstrable proof of communication between the living and the so-called dead, which will survive scientifically applied tests, can be given. Yet he believes in the life after death, and in the possibility of communication between incarnate and discarnate beings. His methods of investigation are directly opposed to those of the spiritualist. His knowledge is the result of personal experience, and not second, or even third hand, as must be the case when a medium, guide and intermediate intelligences