How Plotinus' Soul Animates his Body: The Argument for the Soul-Trace at Ennead 4.4.18.1-9

TLDR: The trace of soul is a quasi-psychic entity that functions as an immanent cause of life for an organism's body as mentioned in this paper, and the trace of the soul must be a cause of the body's life.

Abstract: In this paper I offer an analysis of Plotinus’ argument for the existence of a quasi-psychic entity, the so-called ‘trace of soul’, that functions as an immanent cause of life for an organism’s body. I argue that Plotinus posits this entity primarily in order to account for the body’s possession of certain quasi-psychic states that are instrumental in his account of soul-body interaction. Since these quasi-psychic states imply that an organism’s body has vitality of its own (a claim for which Plotinus also finds support in the Phaedo), and Platonic souls are no part or aspect of any body, Plotinus draws the conclusion that the soul must be a cause of the body’s life by imparting a quasi-psychic qualification to it. In so doing, Plotinus introduces elements of hylomorphism into Platonist psychology, and addresses a problem for the animation of the body that Platonic soul-body dualism may plausibly be thought to face.