No body before the soul: reconstructing Avicenna through al-Ṭūsī and al-Rāzī’s dialectic

According to Avicenna, the soul originates only when the body’s temperament has reached a balanced state. Yet since the temperament is composed of opposing elements, it requires an external principle to unify and maintain it. This raises a difficulty: what unifies and maintains the temperament prior to the soul’s incipience? Fakhr al-Dīn al-Rāzī attributed this role to the mother’s soul, while Naṣīr al-Dīn al-Ṭūsī rejected this view and offered an alternative. I argue that Avicenna himself should be read as holding that the soul originates at conception, with only its vegetative faculties active at first, followed by the gradual actualization of animal and rational faculties. I further propose a new interpretation of al-Ṭūsī as endorsing this conception-view.