There are three premises in the argument:
1. Everything that exists has an explanation of its existence (either in the necessity of its own nature or in an external cause).
2. If the universe has an explanation of its existence, that explanation is God.
3. The universe exists.
Now what follows logically from these three premises?
From 1 and 3 it logically follows that:
4. The universe has an explanation of its existence.
And from 2 and 4 the conclusion logically follows:
5. Therefore, the explanation of the universe’s existence is God.
Now this is a logically airtight argument. So if the atheist wants to deny the conclusion, he has to say that one of the three premises is false.
But which one will he reject? Premise 3 is undeniable for any sincere seeker after truth. So the atheist is going to have to deny either 1 or 2 if he wants to remain an atheist and be rational. So the whole question comes down to this: are premises 1 and 2 true, or are they false? Well, let’s look at them.
According to premise 1 there are two kinds of things: (a) things which exist necessarily and (b) things which exist contingently. Things which exist necessarily exist by a necessity of their own nature. Many mathematicians think that numbers, sets, and other mathematical entities exist in this way. They’re not caused to exist by something else; they just exist by the necessity of their own nature. By contrast, contingent things are caused to exist by something else. They exist because something else has produced them. Familiar physical objects like people, planets, and galaxies belong in this category.
So what reason might be offered for thinking that premise 1 is true? Well, when you reflect on it, premise 1 has a sort of self-evidence about it. Imagine that you’re hiking through the woods one day and you come across a translucent ball lying on the forest floor. You would naturally wonder how it came to be there. If one of your hiking partners said to you, “It just exists inexplicably. Don’t worry about it!”, you’d either think that he was crazy or figure that he just wanted you to keep moving. No one would take seriously the suggestion that the ball existed there with literally no explanation.
Now suppose you increase the size of the ball in this story so that it’s the size of a car. That wouldn’t do anything to satisfy or remove the demand for an explanation. Suppose it were the size of a house. Same problem. Suppose it were the size of a continent or a planet. Same problem. Suppose it were the size of the entire universe. Same problem. Merely increasing the size of the ball does nothing to affect the need of an explanation.
Premise 1 is the premise that the atheist typically rejects. Sometimes atheists will respond to premise 1 by saying that it is true of everything in the universe but not of the universe itself. But this response commits what has been aptly called “the taxicab fallacy.” For as the nineteenth century atheist philosopher Arthur Schopenhauer quipped, premise 1 can’t be dismissed like a hack once you’ve arrived at your desired destination!
It would be arbitrary for the atheist to claim that the universe is the exception to the rule. The illustration of the ball in the woods showed that merely increasing the size of the object to be explained, even until it becomes the universe itself, does nothing to remove the need for some explanation of its existence.
Notice, too, how unscientific this atheist response is. For modern cosmology is devoted to the search for an explanation of the universe’s existence. The atheist attitude would cripple science.
Some atheists have tried to justify making the universe an exception to premise 1 by saying that it’s impossible for the universe to have an explanation of its existence. For the explanation of the universe would have to be some prior state of affairs in which the universe did not yet exist. But that would be nothingness, and nothingness cannot be the explanation of anything. So the universe must just exist inexplicably.
This line of reasoning is obviously fallacious. For it assumes that the universe is all there is, so that if there were no universe there would be nothing. In other words, the objection assumes that atheism is true! The atheist is thus begging the question, arguing in a circle. I agree that the explanation of the universe must be a prior state of affairs in which the universe did not exist. But I contend that that state of affairs is God and His will, not nothingness.
So it seems to me that premise 1 is more plausibly true than false, which is all we need for a good argument.
What, then, about premise 2? Is it more plausibly true than false?
What’s really awkward for the atheist at this point is that premise 2 is logically equivalent to the typical atheist response to the contingency argument. Two statements are logically equivalent if it is impossible for one to be true and the other one false. They stand or fall together. So what does the atheist almost always say in response to the argument from contingency? The atheist typically asserts the following:
A. If atheism is true, the universe has no explanation of its existence.
This is precisely what the atheist says in response to premise 1. The universe just exists inexplicably. But this is logically equivalent to saying:
B. If the universe has an explanation of its existence, then atheism is not true.
So you can’t affirm (A) and deny (B).
But (B) is virtually synonymous with premise 2! So by saying in response to premise 1 that, given atheism, the universe has no explanation, the atheist is implicitly admitting premise 2, that if the universe does have an explanation, then God exists.
Besides that, premise 2 is very plausible in its own right. For think of what the universe is: all of space-time reality, including all matter and energy. It follows that if the universe has a cause of its existence, that cause must be a non-physical, immaterial being beyond space and time. Now there are only two sorts of thing that could fit that description: either an abstract object like a number or else an unembodied mind. But abstract objects can’t cause anything. That’s part of what it means to be abstract. The number 7, for example, can’t cause any effects. So the cause of the existence of the universe must be a transcendent Mind, which is what believers understand God to be.
The argument thus proves the existence of a necessary, uncaused, timeless, spaceless, immaterial, personal Creator of the universe. This is truly mind-blowing!
The atheist has one alternative open to him at this point. He can retrace his steps, withdraw his objection to premise 1, and say instead that, yes, the universe does have an explanation of its existence. But that explanation is: the universe exists by a necessity of its own nature. For the atheist, the universe could serve as a sort of God-substitute which exists necessarily.
Now this would be a very radical step for the atheist to take, and I can’t think of any contemporary atheist who has in fact adopted this line. A few years ago at a Philosophy of Time conference at City College in Santa Barbara, it seemed to me that Professor Adolf Grünbaum, a vociferous atheistic philosopher of science from the University of Pittsburgh, was flirting with this idea. But when I raised the question from the floor whether he thought the universe existed necessarily, he was quite indignant at the suggestion. “Of course not!” he snapped and went on to say that the universe just exists without any explanation.
The reason atheists are not eager to embrace this alternative is clear. As we look about the universe, none of the things that make it up, whether stars, planets, galaxies, dust, radiation, or what have you, seems to exist necessarily. They could all fail to exist; indeed, at some point in the past, when the universe was very dense, none of them did exist.
But, you might say, what about the matter out of which these things are made? Maybe the matter exists necessarily, and all these things are just different contingent configurations of matter. The problem with this suggestion is that, according to the standard model of subatomic physics, matter itself is composed of tiny particles called “quarks.” The universe is just the collection of all these quarks arranged in different ways. But now the question arises: couldn’t a different collection of quarks have existed instead of this one? Does each and every one of these quarks exist necessarily?
Notice what the atheist cannot say at this point. He cannot say that the quarks are just configurations of matter which could have been different, even though the matter of which the quarks are composed exists necessarily. He can’t say this because quarks aren’t composed of anything! They just are the basic units of matter. So if a quark doesn’t exist, the matter doesn’t exist.
Now it seems obvious that a different collection of quarks could have existed instead of the collection that does exist. But if that were the case, then a different universe would have existed. To see the point, think about your desk. Could your desk have been made of ice? Notice that I’m not asking if you could have had an ice desk in the place of your wooden desk that had the same size and structure. Rather I’m asking if your very desk, the one made of wood, if that desk could have been made of ice. The answer is obviously, no. The ice desk would be a different desk, not the same desk.
Similarly, a universe made up of different quarks, even if identically arranged as in this universe, would be a different universe. It follows, then, that the universe does not exist by a necessity of its own nature.
So atheists have not been so bold as to deny premise 2 and say that the universe exists necessarily. Premise 2 also seems to be plausibly true.
But given the truth of the three premises the conclusion is logically inescapable: God is the explanation of the existence of the universe. Moreover, the argument implies that God is an uncaused, unembodied Mind who transcends the physical universe and even space and time themselves and who exists necessarily. What a great argument!