I have chosen the example of the unicorn in order to show how the symbolism of Mercurius is intermingled with the traditions of pagan Gnosticism and of the Church:
The unicorn is not a single, clearly defined entity but a fabulous being with a great many variations: there are, for instance, one-horned horses, asses, fish, dragons, scarabs, etc. Therefore, strictly speaking, we are more concerned with the theme of the single horn (the alicorn)
CW12 ¶ 518A SNOW-WHITE UNICORN
In the Chemical Wedding of Rosencreutz, a snow-white unicorn appears and makes his obeisance before the lion. Lion and unicorn are both symbols of Mercurius. A little further on in the book the unicorn gives place to a white dove, another symbol of Mercurius, who, in his volatile form of spiritus, is a parallel to the Holy Ghost. At least ten out of the fifteen figures in Lambspringk's symbols are representations of the double nature of Mercurius. The picture below shows the unicorn facing a stag (fig. 240) . The latter, as cervus fugitivus, is also a symbol of Mercurius. Mylius illustrates the opus by a series of seven symbols, of which the sixth is the unicorn couched under a tree, symbolizing the spirit of life that leads the way to resurrection (fig. 188) . Penotus gives a table of symbols where the unicorn, together with the lion, the eagle, and the dragon, is the co-ordinate of gold. The aurum non vulgi, like the lion, eagle, and dragon, is a synonym for Mercurius
CW12 ¶ 518Stag and unicorn symbolize soul and spirit
Lambspringk, “Figurae et emblemata,” in Musaeum hermeticum (1625 edn.). Color transcription by Adam McLean.
Tree of the Philosophers
Symbols of the opus surround the tree.Mylius, Philosophia reformata (1622). Color transcription by Adam McLean.
Here I must refer once again to Ripley, where we meet the “green lion lying in the queen's lap with blood flowing from his side.” This image is an allusion on the one hand to the Pietà, on the other to the unicorn wounded by the hunter and caught in the lap of a virgin (fig. 241) , (fig. 242) , a frequent theme in medieval pictures. True, the green lion has replaced the unicorn here, but that did not present any difficulty to the alchemist since the lion is likewise a symbol of Mercurius. The virgin represents his passive, feminine aspect, while the unicorn or the lion illustrates the wild, rampant, masculine, penetrating force of the spiritus mercurialis
CW12 ¶ 519Virgin taming a unicorn
Thomas Aquinas (pseud.), “De alchimia” (MS., 16th cent.) Color transcription by Adam McLean.
Slaying the unicorn in the Virgin's lap
Note the significance of the “wound in the unicorn's side.”Initial from MS. Harley 4751, London
UNICORN AS AN ALLEGORY OF CHRIST
Since the symbol of the unicorn as an allegory of Christ and of the Holy Ghost was current all through the Middle Ages, the connection between them was certainly known to the alchemists, so that there can be no question that Ripley had in his mind, when he used this symbol, the affinity, indeed the identity, of Mercurius with Christ
CW12 ¶ 519THE SERPENT AS AN ALEXIPHARMIC
Like the alicorn, therefore, the serpent is an alexipharmic and the principle that brings all things to maturity and perfection. We are already familiar with the unicorn as a symbol of Mercurius, the transforming substance par excellence which also ripens and perfects unripe or imperfect bodies and is consequently acclaimed by alchemy as salvator and servator
CW12 ¶ 529