One of the major points of contention between atheism and theism in the modern popular debate, is the question of self-existence, or what theology calls Aseity. Modern atheists will often critique theists who say that the universe needs to have an origin, but God can exist on God’s own. The Atheists will often respond that theists give no good reason why God should be able to exist on God’s own, but the universe cannot. This post is an attempt to explain what is meant by self-existence in its theological usage.
In short, self-existence is the property of a thing that exists and does not depend on any other thing for its existence. It does not, as might be thought, mean that a thing causes itself to exist. This would be a logical contradiction. Instead, a being with self-existence has no cause, and simply exists on its own. Because it has no cause, it must exist, for when we look for a cause of its existence, there can be none, and therefore no contingency involved in its being. Thus, if a self-existent being exists, it also necessarily exists.
This should be distinguished from all other things that are not self-existent. A wombat is composite and caused, and thus might not have existed. It has its being in the composite parts and the universe that it exists in. Its being is contingent on its creation in the past. Thus any of these things might have been different, and therefore is neither self-existent nor does it possess necessary existence.
The concept of self-existence is what traditional theism applies to only one thing, God. This is because God is believed to be simple, meaning that God is not made up of many different parts. When we say that God has a mind, and power, and will, we are not saying that God has three different things that are all put together. We are arguing that God, in God’s own being, is wholly and totally simple such that whatever it is that we call “mind” in God is the same thing that we call “being” which is the same thing that we call “power.” However, they are not exactly like what we would call mind, being, and power. For the way we define these things is dependent on definitions that exist within our universe. Mind, power, and being all are categories that we understand as functioning within a physical system. However, when we say that God has mind, power, and will, we are saying that God is something that we do not know, but that is best described with these terms, for we have no others to terms.
Now, when skeptics propose that the universe could be self-existent, we must be very specific about what we mean. It seems that there could be two specific meanings to saying the universe is self-existent.
1. The Material Universe
What some skeptics may mean when they say that the Universe is self existent, is that the whole composite universe of matter and energy, laws, fields, and so on, is itself self existent. If this is the case, then the universe must be necessary. But modern physics does not say that the universe is necessary, or at least not the universe defined like this. Instead, there seems to be a general agreement that the universe as we see it might have been very different if one of a number of different factors had been slightly off, and there is no sense that they must have been the way they were. As well, any system that involves randomness, which they state that the universe has, cannot be necessary as it depends on randomness resulting one way and not another. Thus we see contingency in the universe when it is defined as the whole composite system.
2. The Framework of the Universe
What some other skeptics might mean when they say that universe is self existent, is that the basic framework of the Universe is necessary and not contingent. The very ground of the universe, the laws which determine how things exist, and how they interact, are self-existent. Now this is far better than saying that the material universe is self-existent. However, there are some major problems here as well.
First, we would have to postulate that there is in fact only one real law of the universe that defines how everything exists. If there are multiple laws, we must ask what context they exist in together to interact with the universe. Do they derive from each other? If so, then the multiplicity of laws can exist within the context of the first law, and thus we really have only one law, even if we can identify many elements to it. Now this doesn’t seem to be an insurmountable problem, as many physicists appear to be trying to find the one most basic law of the universe, one that unifies Quantum and Newtonian mechanics.
But what does cause a bigger problem is that that one law, or one law with many emanating laws, does not create matter/energy. The one law determines how matter/energy act and interact, but it does not produce either a context for matter/energy, nor does it produce the matter/energy themselves. There is no indication that the one law of physics has ever produced a single piece of matter, no indication that it has in fact ever caused anything to happen at all. It is a descriptor, and the One Law of Physics, if it exists, will simply describe all objects and events in the universe. For it to have any effect on anything, it must have a universe to work on, it cannot produce it.
Thus we find that even a self existent unified law of the universe, while it could exist, cannot be the origin of the universe…with one possible exception.
If the laws of physics somehow found a way to produce the material universe, we must see that they are outside of the universe. For they cannot be made of matter or energy, or else they are merely the composite contingent universe we described in section 1. But if they are neither matter, energy, nor space, nor time (for these are also part of that composite universe), then they are by definition supernatural. They are outside of the universe in a way that Theists propose that God is.
It is possible that the law behind the universe, the one that determines why things do what they do, is conscious and powerful. If it were conscious and powerful, it could choose to create matter, and be able to do it. It could order all things, determine all things, and have the power to create them. Being conscious, it could choose what laws applied to what objects, and perhaps, sometimes change how the laws apply. Such a Law would also be a Mind, a mind that stands outside of the universe and determines that it should exist.
But then, this is Theism.
 A dubious assertion. Instead, it seems that it would be more honest if they said simply “we do not see why these things happen.”
 Some may see a connection here between this logic and the logic of begetting and procession in the Trinity. They would be right to do so.