Ocellus Lucanus, Firmicus Maternus, Select Theorems of Proclus (Thomas Taylor)

to other things the cause of preservation and permanency, is itself preserved and permanent by its own nature. That, likewise, which becomes to other things the cause of concinnityInternal harmony or agreement., is itself co-harmonized by its own nature. But the world is the cause of existence, preservation, and self-perfection for all other things. The world, therefore, is perpetual and self-perfect by its own nature, has an everlasting duration, and on this very account becomes the cause of the permanency of the whole of things.

In short, if the universe were to be dissolved, it would be dissolved either into that which already exists or into nothingness. But it is impossible that it should be dissolved into that which exists, for there would be no "corruption" of the universe if it were merely dissolved into something that has being; for "being" is either the universe itself or a part of the universe. Nor can it be dissolved into nothingness, since it is impossible for being to be produced from non-being, or for being to be dissolved into non-being. The universe, therefore, is incorruptible and can never be destroyed.

If, nevertheless, someone should think that it may be corrupted, it must either be corrupted by something external to the universe or by something contained within it. But it cannot be corrupted by anything external to it, for there is nothing external to the universe, since all other things are contained within the universe.