Within the depth-psychology corpus, ‘mastery’ operates across at least four distinct registers, each carrying its own valence and theoretical weight. In somatic and trauma-oriented frameworks — Ogden, Levine, Dana — mastery names a hard-won capacity for self-regulation, the restoration of agency to a nervous system that has been overwhelmed; here it is inseparable from the body and is always relational, emerging through therapeutic co-regulation rather than individual willpower. Sri Aurobindo and the Taoist I Ching tradition elevate mastery to a cosmological principle: knowledge of essential causes constitutes genuine mastery, while manipulation of secondary phenomena yields only a simulacrum of control. For Levine in particular, a crucial paradox emerges — true mastery is achieved only through surrender to natural laws, not through forceful conquest. The polyvagal tradition (Dana) sharpens a methodological distinction between discovery and mastery as separable learning phases. Against these developmental or therapeutic usages, Plotinus’s Neoplatonism locates self-mastery at the origin of Being itself, prior to any individual striving. Across traditions, the corpus resists a naive voluntarist reading of the term: mastery is consistently figured as something that opens from within transformation rather than being imposed upon it — a convergence that cuts across ancient philosophical, somatic, and clinical perspectives alike.