The Moon appears on several cards in the Rider-Waite-Smith tarot deck, which is based on astrological associations with the tarot in the teachings of the Hermetic Order of the Golden Dawn. One such card is the Two of Swords.
A.E. Waite instructed Pamela Coleman Smith to use her knowledge of astrology to generate images for the cards. In the Golden Dawn system, Swords represented the Air signs (Gemini, Libra, Aquarius) and the numbers 2, 3 and 4 specifically referred to the three decans of the cardinal signs. Thus, the Two of Swords signified the first decan of Libra, a cardinal Air sign. The image on the Two of Swords in the RWS deck has a strong resemblance to the Justice trump, which is paired with the sign Libra.
The Moon appears on the Two of Swords because this card is associated with the first decan of Libra, which in Chaldean order beginning with Saturn ruling the first decan of Leo (the sign with which the Golden Dawn started the zodiac), the Moon rules the first decan of Libra. Here is the sequence:
Leo’s decans: Saturn – Jupiter – Mars (the 5, 6 and 7 of Wands or Rods)
Virgo’s decans: Sun – Venus – Mercury (the 8, 9 and 10 of Coins or Pentacles)
Libra’s decans: Moon – Saturn – Jupiter (the 2, 3 and 4 of Swords)
Thus, the Two of Swords depicts a woman (the goddess of Justice) blindfolded and impartially holding two swords perfectly balanced despite the pressure of the inconstant Moon, which is affecting the fluctuating emotional tides of the ocean behind her. The character on the card appears to be seeking a balance between opposing opinions or competing ideas as she tries to sort out her feelings about a matter.
Pamela Coleman Smith decided to portray the Moon in its waxing crescent phase, just as it is emerging from an invisible New Moon in which the Moon conjoins the Sun in the element Air (which would be depicted by the Ace of Swords in the tarot). The waxing crescent phase is a time of making new plans and planting new seeds that will grow and then mature at the Full Moon roughly two weeks hence.
The elemental suit of Air stands for our thoughts, ideas, plans, beliefs, opinions, communications both spoken and written, and our efforts to speak the truth. Because Swords are used to represent such matters, there is often an element of battle or conflict. The Aces represent the pure potential of the suit, so that the Ace of Swords stands for new ideas, mental clarity, insight, illumination and the search for truth. The Two of Swords is the earliest concrete manifestation of this potential, which Pamela Coleman Smith depicted as the waxing crescent Moon (emotional currents) in the sign Libra, which represents carefully weighing and balancing ideas and plans before proceeding with a project.
Traditionally this card meant “friendship” perhaps because the Moon symbolizes our emotional attachments, and Libra is tied with social connectedness in a one-to-one manner with those whom we respect and treat as equals. Moon transiting Libra often puts a focus on interpersonal relationships, partnership, teamwork and cooperation with others.
The site CafeAstrology.com delineates Moon passing through Libra as follows:
“Creating order … through pleasing interactions with others and aesthetics in our environment. We tend to solve problems through diplomacy, and we are more able to put aside our own emotions in order to achieve the peace we crave. The tendency now is to avoid direct confrontations. Decisions do not come easily. Seeing both sides to any given situation is the main reason for hesitation. Fear of losing others’ approval is another.”
The sign Libra generally runs from about September 23 to October 22 annually in the tropical zodiac. Thus, this card can sometimes indicate the timing of an event during the first 10 days (the first decan of Libra) of this period.
Below is a diagram of the Moon’s phases from the NASA site.