These three levels of being correspond to those described in the writings of Paracelsus and other alchemists whose work we have studied in the development of our system of constitutional healing. Like past alchemists, Paracelsus looked at the inner subtle constituents that make up all things, which are called Sulfur, Mercury, and Salt. These terms are not to be understood literally, but as states of being or qualities of form which exist in different proportions in all things, in all three realms- plant, animal, or mineral. Sulfur is the soul of a being, which is essential, unique, and eternal. Mercury is the spirit, or life force animating a being, and is the mediator between the other levels.
Salt is the body or container of form, which holds the other principles together.
Paracelsus taught that a balance in the three elements means health, and disease arises from an imbalance in these levels. This imbalance often occurs due to the influence of one or more of the planets. Western alchemical and spagyric philosophy works with the same planetary archetypes found in Qabalah and astrology, as seen in the familiar diagram of the Tree of Life. As in Qabalah, each planetary sphere has individual qualities associated with it, such as deities, colours, musical tones, and days of the week. In spagyric work, each of these planets also rules organs, organ systems, and body parts, diseases and medical effects, and herbs.