Separatio stands as one of the central operations within the alchemical repertoire that depth psychology—above all in the work of Edward F. Edinger—has appropriated as a map of psychic transformation. Where the prima materia presents itself as an undifferentiated, chaotic amalgam, separatio names the necessary act of distinction: the carving of consciousness out of unconsciousness, the sundering of opposites that had lain fused in participation mystique. Edinger draws on mythological, cosmogonic, Gnostic, and alchemical sources with equal authority to argue that separatio is nothing less than the structural precondition for consciousness itself. The Logos, that great discriminating principle, is its primary agent; the cutting edge, the sword, the compass, the scale, and the clock are its instruments. Marie-Louise von Franz contributes the complementary insight that separatio must ultimately be followed by a reunion—the reanimation of the body after the spirit has been differentiated from matter—a movement toward what she terms ‘conscious spontaneity.’ The operation carries inherent danger: wrongly applied, as a mechanical splitting of organic wholes, it becomes destructive rather than generative. The Gnostic Basilides, the Bhagavad-Gita, and the Aurora Consurgens each contribute dimensions to the concept—cosmogonic, soteriological, purificatory—and Jung’s use of Basilides as a motto for Aion underscores separatio’s centrality to individuation theory. The term thus occupies the intersection of epistemology, cosmogony, and clinical practice within the depth-psychology canon.