CHAPTER II. DUALITY AND SUGGESTION. The Doctrine of the Trinity of Man.--The Greek Philosophy.--The Early Christian Fathers.--Hermetic Philosophy.--Swedenborg.--Duality in Modern Philosophy.--"Objective" and "Subjective" Minds.--Their Distinctive Differences and Modes of Operation.--The Subjective Mind a Distinct Entity.--Illustrations from Hypnotism.--Suggestion.--Auto-Suggestion.--Universality of the Law of Suggestion. The broad idea that man is endowed with a dual mental organization is far from being new. The essential truth of the proposition has been recognized by philosophers of all ages and nations of the civilized world. That man is a trinity, made up of "body, soul, and spirit," was a cardinal tenet in the faith of many ancient Greek philosophers, who thus clearly recognized the dual character of man's mental or spiritual organization. Plato's idea of terrestrial man was that he is a "trinity of soul, soul-body, and earth-body." The mystic jargon of the Hermetic philosophers discloses the same general idea. The "salt, sulphur, and mercury" of the ancient alchemists doubtless refers to man as being composed of a trinity of elements. The early Christian Fathers confidently proclaimed the same doctrine, as is shown in the writings of Clement, Origen, Tatian, and other early exponents of Christian doctrine. Indeed, it may be safely assumed that the conception of this fundamental truth was more or less clearly defined in the minds of all ancient philosophers, both Christian and pagan. It is the basis of their conception of God as a Trinity in his personality, modes of existence, and manifestations,--a conception of which Schelling says: "The philosophy of mythology proves that a trinity of divine potentialities is the root from which have grown the religious ideas of all nations of any importance that are known to us." In later times, Swedenborg, believing himself to be divinely inspired, declared that "There appertain to every man an internal man, a rational man, and an external man, which is properly called the natural man." Again, he tells us that there are three natures, or degrees of life, in man,--"the natural, the spiritual, and the celestial." Of modern writers who accept the dual theory, Professor Wigan, Dr. Brown-Séquard, and Professor Proctor are notable examples. Numerous facts are cited by these writers, demonstrating the broad fact of duality of mind, although their theory of causation, based on cerebral anatomy, will not bear a moment's examination in the light of the facts of hypnotic science. In more recent years[1] the doctrine of duality of mind is beginning to be more clearly defined, and it may now be said to constitute a cardinal principle in the philosophy of many of the ablest exponents of the new psychology.