In alchemiy the moon is another androgynous symbol representing the King and Queen in their chemical wedding. The moon also represents silver. Since the moon is illuminated by the sun rays it is also considered feminine.
In Christian iconography the moon represents the Virgin Mary as it represents the Mother Goddess in various traditions of Neo-paganism. Both the Virgin Mary and the Mother Goddess are depicted as standing or enthroned on a lunar crescent. It is no coincidence that the same symbolism represents both the Virgin Mary and the Goddess because they both are equated to the feminine principle. (see Mother)
In ancient tradition, Luna was regarded as a giver of moisture and ruler of the water-sign Cancer, since Cancer is the house of Luna which gives moisture. Furthermore, Luna, having strong influence in alchemical allegory, secrets dew or the sap of life: “This Luna is the sap of the water of life, which is hidden in the Mercurius.” Even the Greek alchemists recognized the moon principle as Christianos called it the “ichor of the philosopher.” Although the influence of the moon was very much stressed since antiquity, it occurs in alchemy expressing a different subtlety. The allegory of dew coming from the moon is still present, but the moon is also the aqua mirifica, that which extracts the souls from the bodies or gives the bodies life and soul. Together with Mercurius Luna sprinkled the dismembered dragon with her water and restores him to life. Considered the water of ablution, the dew falls from heaven and purifies the body making it ready to receive the soul; it produces the albedo, the whitening stage believed synonymous with the philosopher’s stone.
Here again one sees the recurring theme in alchemy, that of death and life. The moon together with mercury sprays her water, dew, on the dismembered dragon and brings it back to life again. It is not surprising that in his Mysterium Lunae Rahner illustrates the extensive use which the Church Father made of the allegory of moon-dew in explaining the effects of grace in the ecclesiastical sacraments. Many of the medieval alchemists practically said the philosopher’s stone was synonymous with God, therefore, Christ, the bestower of sanctifying grace.
Since many alchemists were physicians too, the Greek physician Galen’s views concerning the moon no doubt greatly influenced theirs and left their mark. Galen called Luna the “princeps” who “rightly governs this earthly realm, surpassing the other planets not in potency, but in proximity.” He also claimed the moon was responsible for all physical changes in sickness and health, and regarded its aspects as decisive for prognosis.
Alchemists, many, assumed the ancient belief that the moon promoted growth of plants and gradually developed the peculiar idea that the moon was a plant itself. In the Rosarium Sol is called a “great animal” while the moon is called a “plant.” A.G.H.
Jung, C. G. Mysterium Coniunctions. (Transl. by R. F. C. Hull). “The Collected Works of Jung” Vol. 14. Princeton, NJ. Princeton University Press. 1970. pp. 382, 131-133.
Guiley, Rosemary Ellen. The Encyclopedia of Witches and Witchcraft. New York: Facts On File, 1989. p. 140.