How to prove God does not exist
It has been my observation that the majority of atheists who attempt to defend their atheism choose to defend weak atheism (mere lack of belief in God) rather than strong atheism (the positive view that God does not exist). And among those who actually defend strong atheism, it has been my observation that the majority of them defend it more with bluster than with carefully thought out logical argumentation. It is very refreshing for me to see an exception from time to time. This video attempts to defend strong atheism, and to do it carefully and logically. I really appreciate that.
And since I have such an appreciation for the attempt, I think it deserves a response.
He begins with the law of excluded middle. God is either infinite or God is not infinite. By "infinite" he appears to mean "beginningless." If God is not infinite, then God had a beginning, which means God must've had a cause to his existence, which is clearly unacceptable to most versions of theism, not to mention unparsimonious. So the only viable option for theists (especially Jews, Christians, and Muslims) is that God is infinite, i.e. beginningless. I totally agree with him so far.
The next part is the crux of his whole argument. He argues like so:
1. Actual infinities cannot exist in the universe.
2. God is actually infinite.
3. Therefore, God cannot exist in the universe.
I would take his first premise a step farther and say that actual infinities cannot exist in reality, whether in the universe or not. That would avoid the objection that God does not exist in the universe, which he attempts to answer later in the video.
But the problem with his argument is that it commits the fallacy of equivocation. He is equivocating on "infinity." When he says that infinities cannot exist in the universe, he means there cannot be an actually infinite number of things in the universe. But, of course, when theists say that God is infinite, they do not mean that God is an actually infinite number of things. God is only one thing. Trinitarians say that God is three persons. Personally, I don't know what most theists mean when they say God is infinite, but since the person who made this video equates "inifinity" with "beginninglessness," I can only assume he means that God has existed for an infinite amount of time.
Let's pursue that. To avoid equivocation, he would have to be saying in his first premise that the universe as a whole, as well as everything in the universe, must have a beginning. It cannot have existed for an infinite amount of time, because time itself cannot be infinite, i.e. beginningless. But that presents problems for his argument because he previously argued that if God is not infinite, then God must have a cause, which means God cannot halt an infinite regress. But the same problem is true of the universe. If the universe had a beginning, then by his reasoning, the universe, too, needs a cause. How will he avoid an infinite regress?
There's another problem with his argument. The second premise--that God is infinite--is based on the notion that God is beginningless. Beginningless, then, amounts to an actual infinite. But is that true? If something does not have a beginning, does that mean it has existed for an actually infinite amount of time? I would say not, because if time itself had a beginning, then whatever caused time to begin to exist, cannot have come into existence with time. Since it is causally prior to time, it is beginningless, even though it has only existed for a finite amount of time. And that's exactly what William Lane Craig has been arguing for years. Since it is possible for God to be beginningless, even though God hasn't existed for an infinite amount of time, it is fallacious to invoke the impossibility of an actual infinite to disprove the existence of a beginningless God.
Next in the video, he answers possible objections. He brings up three rebuttals that all basically amount to the same thing--God is not bound by the laws of the universe. Basically what this amounts to is that since "infinities cannot exist" is a law that applies merely to the universe, and since God isn't bound by those laws, that God can be infinite. I agree with him that these rebuttals are fallacious, but disagree with him about why they are fallacious. I think they are fallacious because "infinities cannot exist" is not merely a law of the universe, but a metaphysical law that applies to all of reality, whether in the universe or not. So it won't do to say God can be infinite just because he's not bound by the laws of the universe. It is logic that prevents actual infinities, not the physical properties of space, time, and matter.
But let's look at his rebuttals anyway.
The first objection is that since God is spiritual, he isn't bound by the same things non-spiritual things are bound by--presumably meaning he can be actually infinite even though nothing else can. The rebuttal is that it doesn't matter whether God is spiritual or not, since either way, God is real, and if God is real, then he can't exist within the universe. What exactly is the objection here? I admit I had to think about that for a while. Of course nobody claims that God is part of the universe, so his rebuttal doesn't seem to work at all. Maybe he's objecting to the doctrine of God's omnipresence, since that would require that God is located within the universe. But even if that were true, what has that got to do with the limitations of actual infinities? I confess I don't know.
The second objection is that since God created the universe, he isn't bound by its rules. He says this argument fails because anything in the universe is bound by its rules. If you say otherwise, you are violating the law of non-contradiction. There seems to me to be two problems with this rebuttal. First, the objection does not assume God is in the universe, only that since he created it, he is not bound by its rules. Second, even if the impossibility of actual infinities applies only to the universe, it is far from obvious that it must apply to anything in the universe since it seems at least possible that something which entered the universe from the outside may retain some of its properties. In case I'm not being clear, let me use an analogy. Let's suppose I've got a glass of water. Since water has certain properties (e.g. being a liquid), I can say that anything in my glass has these certain properties of water. But of course it wouldn't follow that anything I put in the glass must also have those properties just because I put it in the glass. Putting a spoon in the glass wouldn't make the spoon a liquid. In the same way, putting God in the universe wouldn't force God to take on all the properties of the universe.
The third objection is that God exists outside of the universe, and is therefore not limited by its rules. His rebuttal is a blatant case of begging the question against God's existence. He simply defines the universe as "everything that exists," and then excludes the existence of God since God is said to be outside the universe. Well, of course if you begin with the assumption of naturalism, you're going to arrive at the negation of anything supernatural, including God. Whether the universe is, in fact, all that exists is the issue under dispute. If God exists, then it isn't true that the universe is the only thing that exists.
In the comment section he responded to one person by saying that several credible sources define the universe as "everything that exists." Well, first of all, that's not a definition of the universe. It's a philosophical point of view about reality. Second, definitions are not arrived at by experts discovering them. Definitions are conventional. Third, as any critic of the ontological argument knows, you cannot define things in and out of existence. Fourth, several authorities define the universe as the sum total of space, time, and matter/energy, not as "everything that exists."