Thus the first being (esse) is for all things the being (esse) by which they are, but not what they are, for it is none of those things which are by participation in it. It is one essence, pure, solitary, separate from and unmixed with all things, yet filling all things like light cast over the universe. By this filling or outpouring, it makes all things reflect it. This is their being (esse), namely, to reflect it, and they can do so only through it, that is, by possessing it, just as air reflects its source of light possessing its source of light insofar as it is possible for the air. It does not have for the sun because its splendor is tied to matter. Hence, it can only be in one matter. The first being (esse), however, is absolute and free through all things, filling and illuminating them by its omnipresence, because no place or matter holds it bound and adhering to it.
William of Auvergne, The Trinity, or The First Principles, Teske & Wade, trs., Marquette University Press (Milwaukee: 1995) p. 89.