chemistry, astronomy and psychology (that is, the psychology in its phase of "brain-action"), the ancients possessed a knowledge of transcendental astronomy, called astrology; of transcendental chemistry, called alchemy; of transcendental psychology, called mystic psychology. They possessed the Inner Knowledge as well as the Outer Knowledge, the latter alone being possessed by modern scientists. Among the many secret branches of knowledge possessed by the Hermetists, was that known as Mental Transmutation, which forms the subject matter of this lesson.
"Transmutation" is a term usually employed to designate the ancient art of the transmutation of metals—particularly of the base metals into gold. The word "Transmute" means "to change from one nature, form, or substance, into another; to transform" (Webster). And accordingly, "Mental Transmutation" means the art of changing and transforming mental states, forms, and conditions, into others. So you may see that Mental Transmuta-