Preconception occupies a remarkable crossroads in the depth-psychology corpus, drawing together epistemological, clinical, and phylogenetic arguments about the mind’s prior structures. The term enters Western thought with Epicurus, for whom the prolepsis — a naturally formed generic notion synthesized from repeated experience — serves as one of the criteria of truth, a pre-theoretical touchstone against which all judgements are measured. The Stoics adopted and refined the concept, distinguishing naturally acquired generic impressions (preconceptions proper) from culturally determined conceptions, and installing them as the very stuff of reason. In the Ciceronian transmission, the innate anticipatio dei becomes evidence that nature itself has implanted knowledge of the gods in all minds. These ancient debates resonate powerfully with modern depth-psychological concerns. Bion’s clinical epistemology, mediated through Money-Kyrle, recasts preconceptions as innate proto-mental readinesses — expectations the psyche brings to experience rather than extracts from it — and explicitly aligns them with Jung’s archetypes as phylogenetic inheritance. Samuels makes this lineage explicit, tracing Money-Kyrle’s preconceptions directly to Platonic Ideas and noting the near-equivalence with Jungian archetypes. Sedgwick’s Jungian clinical voice sounds a cautionary note: excessive preconception in the therapeutic encounter risks ‘psychic murder’, urging epistemological humility. Across all these strands, preconception marks the contested boundary between the given and the acquired, the innate and the cultural.