Within the depth-psychology corpus, Platonic Forms occupy a decisive theoretical crossroads where ancient ontology and modern psychology converge and compete. The term names Plato’s doctrine of eternal, intelligible, unchanging archetypes that serve as the true reality behind sensory particulars — a doctrine elaborated most fully in the Timaeus, where the Demiurge fashions the cosmos after these eternal models. In depth-psychological appropriation, the Forms become philosophically continuous with Jung’s archetypes of the collective unconscious: Edinger makes this identification explicit, reading Platonic anamnesis — the soul’s recollection of Forms known before birth — as the ancient precursor to analytic encounter with collective psychic contents. Tarnas sharpens the conceptual tension between the Platonic position, in which archetypes are ontological principles inhering in the cosmos itself, and the earlier Jungian position, which confined them to the human psyche, arguing that contemporary archetypal astrology restores the Platonic cosmological scope. The Timaeus commentaries (Cornford) furnish the technical philosophical ground, tracing the Forms’ relationship to the Receptacle, to the kosmos noetos, and to the World-Soul. Edinger’s reading of Plotinus further transmits the Forms through Neoplatonism into depth-psychological discourse. What emerges is a corpus-wide tension between Forms as purely psychological structures and Forms as genuinely cosmological realities — a tension that animates the most ambitious theoretical work in the tradition.