The alchemists assumed the existence of three principles in the metals, their obvious reason for so doing being the mystical threefold division of man into body, soul (_i.e_. affections and will), and spirit (_i.e_. intelligence), though the principle corresponding to body was a comparatively late introduction in alchemical philosophy. This latter fact, however, is no argument against my thesis; because, of course, I do not maintain that the alchemists started out with their chemical philosophy ready made, but gradually worked it out, by incorporating in it further doctrines drawn from mystical theology. The three principles just referred to were called "mercury," "sulphur," and "salt"; and they must be distinguished from the common bodies so designated (though the alchemists themselves seem often guilty of confusing them). "Mercury" is the metallic principle _par excellence_, conferring on metals their brightness and fusibility, and corresponding to the spirit or intelligence in man.(1) "Sulphur," the principle of combustion and colour, is the analogue of the soul. Many alchemists postulated two sulphurs in the metals, an inward and an outward.(1b) The outward sulphur was thought to be the chief cause of metallic impurity, and the reason why all (known) metals, save gold and silver, were acted on by fire. The inward sulphur, on the other hand, was regarded as essential to the development of the metals: pure mercury, we are told, matured by a pure inward sulphur yields pure gold. Here again it is evident that the alchemists borrowed their theories from mystical theology; for, clearly, inward sulphur is nothing else than the equivalent to love of God; outward sulphur to love of self. Intelligence (mercury) matured by love to God (inward sulphur) exactly expresses the spiritual state of the regenerate man according to mystical theology. There is no reason, other than their belief in analogy, why the alchemists should have held such views concerning the metals. "Salt," the principle of solidity and resistance to fire, corresponding to the body in man, plays a comparatively unimportant part in alchemical theory, as does its prototype in mystical theology. (1) The identification of the god MERCURY with THOTH, the Egyptian god of learning, is worth noticing in this connection. (1b) Pseudo-GEBER, whose writings were highly esteemed, for instance. See R. RUSSEL'S translation of his works (1678), p. 160.