Breathing occupies a remarkably diverse functional position across the depth-psychology corpus, serving simultaneously as physiological substrate, somatic diagnostic window, therapeutic intervention, and contemplative vehicle. At the neurophysiological pole, Ogden and Fogel map breathing’s automatic regulation through brainstem centers, its bidirectional relationship with autonomic tone via respiratory sinus arrhythmia, and the ways emotional states — terror, grief, rage — distort its ordinary rhythms. Porges and Dana, working within a polyvagal framework, elevate breath to a primary lever for shifting autonomic state: slow, balanced respiration engages the ventral vagal brake, while dysregulated patterns signal and perpetuate sympathetic or dorsal collapse. For clinical sensorimotor practice, Ogden demonstrates that habitual breathing patterns are not neutral habits but active contributors to trauma symptomatology — shallow breathing suppresses emotion, hyperventilation amplifies threat perception — and that carefully graded breathing experiments constitute genuine therapeutic interventions. A wholly different valence emerges in contemplative sources: Watts locates the breath at the precise intersection of voluntary and involuntary action in Zen practice; the Secret of the Golden Flower positions breath-energy as the only available handle for stabilising the restless heart; and Plato’s Timaeus offers an archaic pneumatic cosmology in which inhalation and exhalation enact a universal circular thrust. The central tension of the corpus is between breath as object of technical regulation and breath as threshold to presence — a distinction that clinical and contemplative traditions resolve very differently.