Hēgemonikon
The ruling faculty — heart / chest
The hēgemonikon — 'the commanding part' — is the Stoic unified soul, a portion of cosmic pneuma localised in the chest. Diogenes Laertius VII.159 reports the doctrine plainly: the soul has eight parts, of which 'the principal one is the hēgemonikon, and the others are the five senses, the vocal faculty, and the generative faculty'. All cognition, all judgement, all assent, and all impulse to action originate here; the hēgemonikon is what the Stoic 'I' is. Chrysippus argued cardiocentrism on three converging lines: the voice is felt to issue from the chest, not the head; the affections (anger, fear, grief) register physically in the chest; and the chest is what we strike when we wish to indicate 'myself'. Galen records and ridicules each argument in De placitis II–III. We render the hēgemonikon at mid-sternum, the canonical heart-locus of the Old Stoa, and treat the seven other points as material extensions of pneuma reaching out from this centre.
Point 1 of 9 in Stoic Hēgemonikon — Central Commanding Faculty + Seven Pneumatic Extensions
Cross-tradition overlaps
No overlapping points are registered for this point.
Sources
Diogenes Laertius, Lives VII.159 (primary_canonical)
“The soul has eight parts: the five senses, the generative power, the voice, and the ruling part itself, where the impressions and impulses arise.”
Aetius, Placita IV.21 (primary_canonical)
“The Stoics say that the highest part of the soul is the hēgemonikon, that which produces presentations, assents, perceptions, and impulses; this they call the reasoning faculty.”