Mercury is the smallest planet in our system and the closest to the Sun. It can never be more than 28 degrees longitude away from the Sun so the only astrological aspect the Sun and Mercury can form is a conjunction. Mercury takes 88 days to complete its revolution, which is the shortest of the planets.

Things that change quickly and often are referred to as being mercurial. Mercury is the planet of the rational mind and spiritual direction. Because Mercury represents the rational intellect and the moon represents instinctual memory, when these planets conjunct, superior intellect occurs, because the native has superior ability to remember everything he or she learns.

The mythology of Mercury begins back in Babylonian times where Mercury was known as Nebo (Nebu). Nebu was the son of Marduk, the king of the gods. Marduk became the king by slaying the sea monster Tiamat, who represented chaos, thus establishing order in the universe. Nebo became the scribe of the gods. It was his job to write down the laws and edicts of Marduk and to communicate them to men. Marduk later evolved into the Greek ruler of the gods, Zeus and then the Roman Jupiter. Nebo evolved into Hermes and then, Mercury.

The most significant observance of the Babylonian calendar was the Babylonian New Year festival, which recreated the battle of Marduk against Chaos. During this festival, the image of Nebo was ceremonially removed from its shrine in Borsippa and carried to the temple of Marduk in Babylon. Through this act of Nebo being symbolically joined with his father, it was established that Mercury (Nebo) served Jupiter (Marduk). This ceremonial enactment represents the link of an individual's mind with his sense of purpose.

Hermes was the Greek god of communication and also the god of thieves. Hermes was the son of Zeus and Maia, a nymph and was born in a cave at the top of Mt. Cyllene in Arcadia. As an infant he was well-established as a thief. When he crawled out of the cave, the first thing he saw was a tortoise. He promptly took the shell of this creature and created a lyre. He is thus credited with creating the first musical instrument. He then stole some cattle from Apollo and when found out he was taken up to Zeus for judgment. Both Zeus and Apollo were impressed with the infant's extreme intelligence. Hermes returned the cattle and as a gift of reconciliation he gave Apollo the lyre. Later, the lyre became the symbol of Apollo, as the god of music. Apollo gave Hermes the job of transporting souls from this world to the next, a divine function that had previously been performed by the sun god, Helios. Interestingly, the Egyptians called Hermes, Thoth, and his role in Egyptian mythology was as the transporter of souls.

Because the human intellect is by itself, amoral, and its function is rational thought, not necessarily connected to an ethical code, the same mental process that leads a person to write a great classic may lead another to lay the plans and carry out a flawless robbery.

Mercury is also the patron of merchants. Herein lies another important connection between Mercury and Jupiter: the mind only becomes a strong force for good when directed by a higher sense of awareness. An afflicted Mercury is always found in the birth chart of a career thief.

Mercury is always associated with youthfulness. His activities began on the day of his birth. He was well-established by reputation in his youth. The Peter Pan complex is associated with an afflicted Mercury in the third house.

Third house Gemini/Mercury can indicate a highly creative or a completely underdeveloped native...and sometimes BOTH. They can move through life with the charm of a child and without noticeable purpose...always making plans, but never being able to bring them to fulfillment.

As the escort of souls, the archetype of Mercury has always involved movement and travel. Mercury is, after all, mercurial and speed was associated with him as the messenger (carrier of communications) between the gods.

Mercury also possessed the caduceus, the healing rod that is featured as the symbol of the medical profession. Until modern times, the mind and body were treated as a unity. Holistic medicine is the only medical art/science that causes healing to occur by treating the cause of the symptom, not just the symptom itself. Holistic medicine works by refocusing the mind and body through thought and action rather than treating the symptom only, as the current allopathic medical practice does. Mercury possessed the caduceus because without the mind's involvement in the healing process, healing cannot take place. True healing only occurs when the mind and body are in alignment.

Intellect must be linked with a sense of direction which is will. Hence the connection between Mercury and the Sun. When the Sun and Mercury conjunct to within one degree of each other Mercury is said to be "combust" meaning the brightness of Mercury is lost in, or combined with, the glow of the Sun. That can mean one of two things: a person can either be given an extremely focused, intense sense of direction or, it can mean that under pressure the person is not able to focus at all and must stop, step back, and take time to refocus. Further, when Mercury is out of sign or several degrees away from the Sun, there can be a distinct difference in the person's thought patterns. Someone with this kind of separation between intellect (Mercury) and body (Sun) is said to have a mind of his own. There is a distinct disconnection between the mind and the will or self. I knew one person who had an out-of -house placement between Mercury and Sun in his chart and he created a totally separate life...complete with people and places and events with people he knew online from what he was experiencing in his everyday life. He COMMUNICATED about this life, but did not live the life he talked about. When I found out about this I was amazed at his ability to keep the two separate and distinct from each other and this, taking no other planet placement into account.

As the planet of spiritual direction, Mercury is often ignored. Mercury was the conductor of spirits from this world to the next and was the only being that could travel freely between the two worlds. Mercury's placement can indicate the path on which spiritual direction will move. Mercury also endows people to be able to use the power of the mind to travel anywhere ...the limits of which are entirely of one's own making.

Sources:

Mythic Astrology: Archtypal Powers in the Horoscope by Ariel Guttman and Kenneth Johnson

Mythology by Edith Hamilton