The Moon occupies a position of singular complexity within the depth-psychology corpus, functioning simultaneously as cosmological symbol, archetypal image, psychological function, and astrological significator. Across the library’s major voices — Jung, Greene and Sasportas, Moore, Rudhyar, von Franz, Pollack, Nichols, and Cunningham — the Moon consistently marks the domain of cyclical change, instinctual embodiment, and the pre-egoic substrate of personality. Jung’s seminars establish the Moon’s three phases as a morphology of psychic rhythm, linking lunar waxing and waning to archaic emotional life and the anima principle. Greene and Sasportas extend this into astrological psychology, reading the natal Moon as the ‘primal substance on which the personality is built’ — the vessel of bodily reception, childhood imprinting, and the mother complex. Moore, drawing on Ficino, emphasises Luna’s reflective character and the cultivation of a consciousness attuned to beginning, fullness, and emptiness as a rhythm rather than a goal. Von Franz and Jung both locate the Moon within alchemical symbolism, where it stands opposite the solar principle in the fundamental duality of psychic life. The tension between the Moon’s paradoxical nature — reliable in cycle yet treacherous in moment — and the ego’s desire for stable illumination constitutes one of the corpus’s enduring dialectics.