First I will discuss the underlying divine reality, and afterward the divine essence. These two might seem to be one and the same thing, but underlying reality is even more universal than essence. Essence presupposes an underlying reality and arises from it. The underlying reality of God, the underlying divine reality, cannot be described. It is beyond the reach of any idea in human thought. Everything human thought can conceive of is created and finite; it cannot conceive of what was not created and is infinite. Therefore it cannot conceive of the underlying divine reality.
The underlying divine reality is the reality itself from which all things exist, and which must be in every thing in order for that thing to exist.
Some further notion of the underlying divine reality may, however, be gained from the following points:
1. The one God is called Jehovah from “being,” that is, from the fact that he alone is and was and will be, and that he is the First and the Last, the Beginning and the End, the Alpha and the Omega.
2. The one God is substance itself and form itself. Angels and people are substances and forms from him. To the extent that they are in him and he is in them, to that extent they are images and likenesses of him.
3. The underlying divine reality is intrinsic reality and is also an intrinsic capacity to become manifest.
4. The intrinsic, underlying divine reality and intrinsic capacity to become manifest cannot produce anything else divine that is intrinsically real and has an intrinsic capacity to become manifest. Therefore another God of the same essence is impossible.
5. The plurality of gods in ancient times, and nowadays as well, has no other source than a misunderstanding of the underlying divine reality.
These points need to be clarified one by one.
from True Christianity, Volume 1, Section 18