The Play System occupies a significant and theoretically generative position within the depth-psychology corpus, examined from neurobiological, developmental, somatic, and mythological vantages. Panksepp’s foundational contribution in affective neuroscience establishes PLAY as a discrete primary emotional system with identifiable subcortical circuitry — not reducible to exploration, aggression, or sociability, but constituting an autonomous motivational architecture of the mammalian brain. This distinction is taken up by Ogden, who integrates Panksepp’s findings into sensorimotor psychotherapy, insisting that play is ‘an action system in its own right’ characterized by spontaneity, intrinsic pleasure, and freedom from overwhelming affect. Dana and Porges situate the Play System within polyvagal theory, identifying it as a ventral-vagal-mediated state that co-opts the mobilization defense system for safe social engagement — a neurophysiological maneuver with profound clinical implications. For trauma therapists, play emerges as both a diagnostic window into autonomic history and a restorative practice requiring careful titration of ‘neural challenge.’ Van der Hart introduces a darker clinical register, where play action systems in dissociative clients may serve simultaneously as sequestered pleasure and as psychological defense against traumatic realization. Campbell’s mythological inflection — play as cosmological lîlâ, as the spirit’s voluntary entry into world-game — extends the concept beyond developmental neuroscience into questions of meaning, civilization, and transcendence.