Mercury is a universal alchemical symbol and in most cases that of the passive, moist principle, yin. In alchemical terms, ‘solution’, bringing back to mercury again, is regression to an undifferentiated state. Just as a woman submits to the male, so mercury is subservient to sulphur. Mercury, the Chinese ‘liquid silver’ (chui-yin), corresponded to the dragon, the bodily fluids blood and semen, the kidneys and the element Water. Western alchemists set mercury in opposition to sulphur, but the Chinese brought them together as cinnabar. The rotation of mercury and cinnabar obtained by successive calcinations is that of yin and yang, of death and rebirth. Some Western alchemical traditions maintain that mercury is female and sulphur male semen and that metals are born of their subterranean coitus.
In India, on the other hand, mercury was regarded as a concentration of solar energy underground, Shiva’s semen to which mercurial lingams were dedicated. Mercury has the power of separating gold. It is a food of immortality, but also a symbol of deliverance. Alchemical mercury is a symbol of soma, which Tantrism uses to govern secretion and circulation. It may well be the means by which this deliverance is effected through strengthening the body. ‘Mercury Knowledge’ is in any case a term for a science of inward regeneration which we know by the name of Yoga. Mercury was believed to be able to obtain pure gold, as Yoga immortality.
In astrological analysis Mercury comes immediately after the two great lights the Sun, planet of life, and the Moon, planet of birth, in other words of the manifestations of life in our ephemeral world. If the Sun is the Heavenly Father and the Moon the Universal Mother, then Mercury is their child, the Intercessor. His two houses, that is to say the two signs of the Zodiac with natures most in harmony with that of this planet, are Virgo, which follows the solar sign, Leo, and Gemini, which comes before the lunar sign, Cancer.
Being the nearest neighbour to the Sun, Mercury is the swiftest planet, ceaselessly spinning. Mercury, the busy mythological god with wings at his heels, was the messenger of Olympus. This is as much as to say that Mercury is basically a principle of liaison, communication, movement and adaptation.
If one goes on to observe that the caduceus is Mercury’s attribute, one will readily appreciate the twofold nature of this symbol, in which the opposing yet complementary principles of light and dark, high and low, left and right, male and female meet head on. This internal ebb and flow comprises the first stage in intellectual development - distinguishing differences to avoid confusing one thing with another and standing outside oneself. Such interplay helps strengthen the rational by reducing reliance on instinct and repressing purely sensory responses. On these foundations, the structure is built of the socialization of the individual through acceptance of custom and submission to the laws of logic, the intercommunication of ideas clothed in words and of physical objects by a regulated system of exchange. In every individual the Mercurian process assists the ego to divert us from the attractions of a subjectivity which keeps us in darkness. The process pushes us to the point where the world around us comes together in a network and wealth of contacts. Mercury is the best channel for adapting to life in the face of the twin pressures of internal drives and external stimuli.