Hegemonikon
The hegemonikon (Ancient Greek: ἡγεμονικόν, romanized: hēgemonikón, "ruling part") is a term in ancient Greek philosophy of mind for the soul's governing or commanding faculty, the part responsible for sensation, judgment, impulse and assent. Although the word had earlier use, the doctrine was most fully developed by the Stoics of the third century BCE, who held that the rational soul is a single, unified hegemonikon located in the heart and identified with the highest grade of pneuma.