Regulation stands as one of the most structurally load-bearing concepts in the depth-psychological corpus, appearing at the intersection of neurobiology, developmental theory, clinical practice, and philosophy of mind. The literature distributes across several distinct but converging registers. In the neurobiological register — represented most prominently by Schore, Porges, and Siegel — regulation designates the capacity of the organism to modulate arousal states, autonomic tone, and affective intensity, with particular emphasis on how early relational experience literally sculpts the brain’s regulatory architecture. Porges frames regulation through vagal tone and the polyvagal hierarchy; Schore anchors it in orbitofrontal-limbic circuitry and dyadic mother-infant transactions; Siegel integrates both into a broader account of how relationships and neural integration co-constitute regulatory capacity. A second, clinically applied register — DBT skills literature, body-oriented therapy, polyvagal-informed practice — treats regulation as a teachable skill set: emotion labeling, mindfulness, interoceptive awareness, and co-regulation protocols. A third, philosophically inflected register reaches back to Plato’s civic concern with ordered conduct. Across all registers, the fundamental tension is between self-regulation as an intrinsic achievement and co-regulation as its necessary precondition — a dialectic that organizes both developmental accounts and therapeutic strategy.