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

For every thing which can in any way whatever be dissolved and destroyed, is either corporeal and a composite, or is allotted its hypostasis in a subject. And that indeed, which is dissolved, is corrupted as consisting of many things. But that which is naturally adapted to be in another thing, vanishes into non-entity when separated from its subject. Moreover, the soul is incorporeal, and external to every subject, subsisting in itself, and being converted to itself. Hence, it is indestructible and incorruptible.