Within the depth-psychology corpus, ‘dark’ functions not as mere absence of light but as a charged psychic category encompassing the unconscious, the chthonic, death, and the preconditions of transformation. The term sustains at least four distinct theoretical registers. First, in the Greek imaginal tradition recovered by Padel, darkness is the ontological medium of the underworld, of prophetic consciousness, and of alternative knowing: the mad see ‘otherwise’ precisely because their innards are darkened, and Heraclitus himself is skooteinos. Second, in Jungian and alchemical psychology—developed most systematically by Hillman—the dark is the nigredo, the blackest phase of the opus, simultaneously a paradigm-breaker and the most dangerously literal state of soul; it is placed within a color sequence precisely because it must not become a terminal identity. Third, in Chinese cosmological thought as mediated through Wilhelm’s I Ching, dark and light are the two primal powers whose alternation constitutes the Tao itself; neither is merely privative. Fourth, in Freudian-inflected analysis (Abraham), darkness carries the unconscious valence of the womb, a regressive symbolic field. The tensions among these positions are productive: whether darkness is epistemically generative or psychically lethal, whether it is to be inhabited or traversed, whether it names a cosmological principle or a clinical danger, remains actively contested across the library’s major voices.