One God

The most fundamental principle of Theism is the belief in a single God, as opposed to the many gods of pagan religions. This is why Theism is often called monotheism. The belief in a single God is not an arbitrary thing, rather, the very definition and understanding of God according to Theism means that there can only be one of Him.

When God appeared to Moses in the burning bush, He gave him a definition of Himself as Being Itself. His words have often been translated into English as “I am who Am,” but a better translation would be, “I am Am,” or “I am Being.” This was a radically different conception of divinity than had come before. The pagan peoples’ various pantheons were populated by gods who were rather like super-humans, but God wished to define Himself as beyond these conceptions, and St. Thomas Aquinas’ study of what it means to be Being Itself shows clearly how far removed He is from such limited imaginings.

That God is Being Itself, Thomas explains, means that God is the same as His existing, that His essence and his existence are identical. This is a hard concept for us to grasp, creatures that we are, because our own existence is predicated, dependent, and therefore outside of our essence. But God, since He is Being Itself, holds His existence in Himself, and does not receive it from anything else. He alone possesses independent being. This could not be the case if his existence were not identical with his essence.

Since God is Being Itself it follows that He is perfect. A thing or process is perfected when it has attained the summit of it’s existence. For instance, the process of germination is perfected when a seed sprouts, and the resulting plant is more perfect than the un-sprouted seed, since it is closer to its proper existence as a plant. It can be explained in terms of potentiality and actuality: the seed had the potential to sprout, and this potential has been actualized, and since there is less potentiality, and more actuality, of the plant being what it is intended to be, it can be called more perfect. God is truly perfect, that is to say, He contains no potentiality at all; He is pure actuality. This is consistent with our knowledge that God is Being Itself, because Being Itself could not have potentiality or it would have an incompleteness in its being, a lack, and therefore could not be called Being Itself.

So we have established that God, as Being Itself, is perfect. He is complete in Himself, that is, He has no potentiality but is all actuality. We can apply this knowledge to the question of whether there is one God. It follows that there is. If there were another God, it could not truly be God, because God is, by definition, Being Itself. There cannot be two of Being Itself; that is a contradiction. If there were, one being would have a lack of the being of the other. This lack would be a potentiality, and therefore an imperfection, and we have already demonstrated that Being Itself can have neither potentiality nor any imperfection. Being Itself cannot lack Being, because it is wholly complete in its Being.

One might argue that the existence of humans, or of any Being other than God, demonstrates that there is existence that is not God, therefore the above argument does not stand. But our existence is, as I have mentioned before, predicated upon God, that is to say, He holds our existence as well as His own, and it is His will that keeps us in existence from moment to moment. But if there were another God, another Being Itself, its existence would not be predicated upon the other God, or it would not be a God, a Being Itself. There cannot be two unpredicated existences, because an unpredicated existence has no lack or potentiality, and the existence of another unpredicated existence would be a lack or potentiality of being, since the first unpredicated existence could potentially have the existence of the other unpredicated existence.

One might argue further that the Christian belief of the Trinity contradicts this truth that there can be only one unpredicated existence. However, the three persons of the Trinity, while distinct and separate from each other, share the same nature, the same divine essence, which is that unpredicated existence, Being Itself. This is a profound mystery of the Christian faith, but though we cannot fully understand how it may be, we can nevertheless understand that the Trinity as it is defined does not contradict the idea of there being a single unpredicated existence, a single God.