Mercury

Mercury is one of the tria prima, the three philosophical principles that the physician and alchemist Paracelsus (1493-1541) set at the root of all substances, alongside Sulphur, Mercury and Salt. It stands for the spirit, the volatile and fluid principle; the quality of quicksilver, of consciousness and connection, that carries and mediates between the other two.

The three principles

Paracelsus taught that every material thing is composed of these three, whose balance accounts for its nature: Sulphur the soul, Mercury the spirit and Salt the body. In the scheme of correspondences the principle is linked with Mercury.

These principles are not the ordinary substances that share their names; they are qualities or philosophical elements. They are described here as part of the documented tradition of European alchemy and Paracelsian medicine, in which they became a standard framework for thinking about matter and transformation.

Sources The Secrets of AlchemyLawrence M. Principe with Paracelsus: An Introduction to Philosophical Medicine in the Era of the RenaissanceWalter Pagel

Mercury is the other half of the older pair, and the ambiguity in its name caused more confusion in the literature than any other single term.

The two-principle theory

The doctrine that metals are compounded of a sulphur and a mercury reached Latin Europe from the Arabic alchemical tradition through the translations of the twelfth and thirteenth centuries. Within that theory Mercury supplies fluidity, volatility and the metallic character, and Sulphur supplies combustibility and form. Adjusting the proportion of the two accounted for the differences between metals, which is what made the transmutational programme look tractable.

Three different things under one word

Alchemical texts use the word for the philosophical principle, for quicksilver the actual liquid metal, and for a prepared substance the author claims to have made and will not name. Writers were aware of the ambiguity and some exploited it deliberately, since a treatise that could be understood by an adept and not by anyone else was doing what its author intended.

That deliberate obscurity is a genuine feature of the corpus and not a failure of the modern reader.

How a third arrived

Salt was added as a third principle in the sixteenth century by Paracelsus, producing the tria prima. That addition is datable and attributable, and it extended a theory of metals into a theory of all bodies.