The number three occupies a densely contested position in the depth-psychology corpus, functioning simultaneously as a structural rhythm, a symbolic inadequacy, and a theological-psychological index. Jung’s central claim—developed across the alchemical writings, the Trinity essays, and the seminar literature—is that three is not a symbol of wholeness but of dynamic polarity: every triad implies its opposite triad, generating the tension of opposites that wholeness, symbolized by four, alone resolves. This thesis is sharpened by the recurrent observation that three and four stand in unresolved alternation throughout alchemy, mythology, and the unconscious itself. Von Franz, approaching the question through fairy-tale analysis, maps the phenomenology precisely: fairy tales proceed in rhythms of three similar episodes followed by a qualitatively different fourth—a structural grammar that exposes the limitation of threeness even as it exploits its momentum. Edinger elaborates the same pattern through Hegel’s dialectic and through developmental psychology, reading three as the number of ego-consciousness assaulting original wholeness. Mythologically, triads of goddesses (Hecate, the Moirai, the triple lunar aspects) and theological trinities (Christian, Daoist, alchemical) populate the corpus, confirming the archetype’s cross-cultural reach. The tension between three as dynamic becoming and four as achieved totality remains the organizing problem of the entire discussion.