Putrefaction — rendered in alchemical Latin as putrefactio — occupies a structurally indispensable position within the depth-psychological reading of the opus alchymicum. Across the corpus, from Jung’s foundational equating of the operation with psychological dissolution to Edinger’s meticulous clinical mapping and Hillman’s imaginal phenomenology, putrefaction is consistently positioned as the necessary decomposition that precedes any genuine transformation. It is not merely one operation among many but a threshold condition: the blackening, the stench, the breaking of inner cohesion that the corpus insists cannot be bypassed if new life is to emerge. Jung, citing Aristotle — ‘Nunquam vidi aliquid crescere sine putrefactione’ — anchors the concept in nature’s own grammar of renewal. Edinger situates putrefactio within the broader mortificatio complex, distinguishing it precisely as ‘rotting,’ the dissolution of organic structure, and traces its biblical resonances (John 12:24, the grain of wheat) and its modern psychological equivalents: dreams of overflowing toilets, worms, air pollution. Hillman, characteristically, insists that putrefaction is itself a mode of awareness — sulfur experiencing its own wound, decay as a form of sophistication — resisting any merely developmental or teleological reading. Abraham’s lexicographic work anchors the imagery concretely: the blackened toad, the flood, the grave-vessel, the forty days of dissolution. The term thus condenses the corpus’s central wager that psychological transformation requires genuine death, not mere regression.