Within the depth-psychology and sinological corpus catalogued in this library, yin emerges not as a simple negative pole but as a complexly valenced principle whose meaning shifts according to cosmological register, alchemical context, and ethical orientation. Alfred Huang’s exposition of the I Ching establishes the foundational tension: yin is simultaneously a positive complement to yang — yielding, responsive, cooperative — and, when it competes against rather than harmonizes with yang, the source of viciousness and disorder. Richard Wilhelm’s rendering of The Secret of the Golden Flower situates yin within the Taoist metaphysics of Tao as the pre-divided ground from which the opposition of yin and yang arises into reality. Liu I-ming, in the Taoist I Ching, converts cosmological yin-yang polarity into a soteriology of inner alchemy: yin represents the mundane, the conditioned, and the force that gradually strips away yang vitality; yet it is also the medium through which the adept, working in ‘reverse operation,’ preserves and completes yang. Hellmut Wilhelm traces the symbolic history of yin from mythological animal imagery — the mare, the cow — toward increasingly abstract cosmological concepts. Richard Wilhelm’s I Ching commentary adds an existential register: yin is the realm of fixed number, daemonic necessity, and rigid determinism, as against yang’s living, mutable light. The central tension throughout is whether yin is primarily complementary or oppositional — a question the corpus never finally resolves but holds in productive dialectical suspension.