"To believe is to reflect, to know is to penetrate."

Robert Fludd

The Moon archetype is the 18th key in the Tarot Arcana and is represented astrologically by the mutable water sign Pisces. Pisces is associated with the collective unconscious, the transpersonal, dreams, unknown fears, confinement, and insanity. Pisces is the last sign of the zodiac and represents the culmination of the the preceding eleven signs.

The attribution of the Tarot Moon to Pisces is significant because Pisces is where the boundaries of the socialized self begin to dissolve, opening into the awareness of a deeper transpersonal sense of self. From early childhood the training of the intellect involves  learning to segregate ideas, people, and things, establishing an I-thou relationship with objective reality. Ideas, language, and preconceptions work to define and protect the ego, helping it sustain a sense of autonomy and personal awareness. The Moon represents an entry into the mysteries of the unconscious, wherein  rules, form, and egoic boundaries are no longer secure, but struggle to maintain primacy. The Moon prompts without words or familiar sights of the day, she leads into the dark  chthonic waters of the unconscious wherein the doorways to both madness and illumination reside.