The term ‘atom’ appears across the depth-psychology corpus in three distinct registers, each carrying its own theoretical weight. The oldest and most philosophically consequential usage derives from classical atomism — Democritus, Epicurus, and their Hellenistic inheritors — where the atom figures as the irreducible, indivisible particle whose chance encounters (via the clinamen) constitute composite individuals. Simondon subjects this tradition to its most searching critique, arguing that atomistic substantialism, by grounding individuation in a pre-formed principle, forecloses genuine account of individuation as process (ontogenesis). For Simondon, the atom exemplifies the foundational error of positing the individual as already-given rather than as the outcome of a metastable becoming. A second register appears in the philosophy of nature running from Plato’s Timaeus through modern physics: Cornford’s commentary insists that Plato’s geometric corpuscles are emphatically not atoms in the Democritean sense, since Platonic space is a recipient, not a void. A third, more culturally diffuse usage appears in mystical poetry cited by Campbell, Harvey, and Attar — ‘the world’s wild atoms’ as a metaphor for the irreducible particulars of phenomenal reality that rational vision cannot penetrate. Pauli and Ponte connect atomic physics to depth-psychological questions about consciousness and the psychophysical problem, suggesting that the post-classical atom has become a locus for negotiating the boundary between matter and psyche.