Unity of Soul to Avicenna and Thomas Aquinas

The question of plurality or unity of human soul is among the topicswhich basically originate from Plato's and Aristotle's works. Platoconsiders the subject from two approaches and finally accepts theplurality whereas Aristotle deems it unreasonable to reckon the soul tobe plural and divisible and consequently admits the unity of the soul.Regarding these two theories (i.e. the unity of the human soul and theplurality of it), the philosophers have to either confirmed one theoryand reject the other at the same time. Therefore the two PeripateticIslamic and Christian philosophers, Avicenna and Thomas Aquinas areinclines toward the “unity of soul “theory. The difference of these twophilosophers is in that Avicenna’s requires clarifications due to someconflicting aspects in his theory. This conflict arises from therepeatedly emphasis on soul unity on one hand and in the meantimeattribution of human activities to three other souls. To integrate theseevidently clashing points it is possible to set forth two status namely“definition and realization” (essence and existence). Aquinas assessesthe subject more rigorously and in more detail comparing to Avicennaand while considering different views including Plato’s, proves thedominance of Aristotle's theory over Plato’s.