The Six Books of Proclus on the Theology of Plato, Volume 2

For if something pertaining to the soul remained on high in the intelligible world, it will always perceive intellectually, without transition or transitively. But if without transition, it will be intellect, and not a part of the soul, and this partial soul will proximately[324] participate of intellect. This, however, is impossible. But if it perceives intellectually with transition, from that which always [and from that which sometimes[325]] energizes intellectually, one essence will be formed. This, however, also is impossible. For these always differ, as has been demonstrated. To which may be added, the absurdity resulting from supposing that the summit of the soul is always perfect, and yet does not rule over the other powers, and cause them to be perfect. Every partial soul, therefore, wholly descends.