Plotinos: Complete Works, v. 2 In Chronological Order,...

3. It might be objected that nothing (in all this) would hinder the first Principle from being both single and manifold. We will answer that the manifold needs a single subject. The manifold cannot exist without the One from which it comes, and in which it is; without the One which is counted the first outside of other things, and which must be considered only in itself. Even on the supposition that it co-exists with other things, it must, none the less, while being taken with the other things with which it is supposed to co-exist, be considered as different from them. Consequently, it must not be considered as co-existing with other things, but be considered as their subject (or, substrate), and as existing in itself, instead of co-existing with the other things of which it is the subject.