There are three versions of this argument: the argument from causation in esse, the argument from causation in fieri, and the argument from contingency.
<The following is a portion of Larrys Text, wikification is invited>
But let's leave the discussion there and look at a second argument for the existence of God, namely, the cosmological argument, also known as the first cause argument for the existence of God. Thomas Aquinas, the most famous philosopher of the Middle Ages, had a simple version of this argument.
The cosmological argument infers the existence of God from claims about the entire universe. The basic idea is that God must exist since the entire universe needs a cause; the very existence of the universe requires some explanation, and an act of God, namely creation, is that explanation. So let me present the argument.
Consider some event in the universe -- let's say, the fall of the Berlin Wall. It had to have a cause, no doubt a very complex cause, but some cause. Such as protests in East Berlin; they helped cause the fall of the Wall. But then of course those protests in East Berlin had to have some cause. And those causes had some causes, and so forth. There is one enormous chain of events in the universe, with the earlier events causing the later events. So now we have to ask ourselves: Did this chain of causes have a beginning? Yes or no?
Let's not try to resolve that question now. But rather than just assume that the universe had a beginning, let's just ask: Did this chain of causes making up the universe have a beginning? Now, our conclusion is going to be the same whether we say "Yes" or "No."
So suppose on the one hand that there was a first event, which started the entire chain of causes and effects which make up all the events in the universe. Astronomers today commonly think that there was such an event, called the "Big Bang". The universe began with an enormous explosion of matter and energy from a superdense point. But then of course the Big Bang was another event in the universe. If we say it is "the first event" we still want some explanation for the event. Why did it happen? It had to have some first cause. We call this first cause, the thing that caused that first event, God. God created the universe; so God exists.
Now let's suppose on the other hand that there was no first event; the universe has already existed an infinite amount of time, and will continue to exist an infinite amount of time. Nevertheless we might ask: Why is there something rather than nothing? (This is Leibniz's famous question.) Why is there this particular whole infinite chain of causes and effects, rather than some other chain, or no chain at all? There has to be something that explains this. What? Evidently whatever explains it has to be something that is necessary in itself, which carries the explanation for its own existence in itself, as it were. So we can say that a necessary being, that caused the universe, exists. This being we call God; hence God exists.
So we come to the same conclusion, that God exists, whether or not we suppose there was a first event in the universe. Therefore, God exists.
Well, is this argument any good? A lot of believers have thought so. But, not surprisingly, it has been subjected to some very hard objections. Again, we are just going to review a few of the objections that philosophers have raised. Even if you think that none of these objections succeed, they do at least have the effect of clarifying exactly how the argument is supposed to go.
First objection. Remember that in the argument as I presented it, either the universe had a first event, or has existed from eternity. So suppose that the universe had a first event. According to the cosmological argument, this first event had to have some cause -- which means, some event which caused the first event. Now can we even make any sense of that? The proposal is: there was a first event; but this first event had to be caused by another event. But don't causes have to precede their effects? Surely. But then what we are calling the "first event" is not actually the first event, because there is another event, which preceded it and caused it to occur -- and that is a contradiction.
Well, you might say, that objection is no good, because by the words "first event" we mean first event in the physical universe. We can say that the cause of the first event in the physical universe, namely, God's act of creation, is not itself in the physical universe. It was a spiritual act, which resulted in the first physical event.
Second objection. But then we ask: why think that there had be a cause, spiritual or otherwise, of the first event? Why can't there be an uncaused event? What people are likely to say is that the very notion of an uncaused event is absurd; and so they enshrine their view about causality in something that has been called the Principle of Causality. The Principle of Causality is simply that every event has a cause; there is a cause of everything that happens. Now, we could talk about this principle for a long time; but for our purposes, suffice it to say that a lot of philosophers do not see why this so-called Principle of Causality has to be true at all. Isn't it at least possible that an event, especially an event like the Big Bang, might not have a cause at all, but that it simply exists? If you think that it's impossible that the Big Bang didn't have a cause, the question for you is: where is the contradiction in saying that there was no cause? In other words, why do you think the Principle of Causality is always true? Perhaps you might come up with an argument for it. Or perhaps you will just stubbornly maintain that it can and indeed must be held without any argument. We could talk about that a lot more, but let's leave that discussion there.
Now this second objection applies only to the case where the universe had a first event. What about the case where the universe has existed from eternity? That brings us to the:
Third objection. If you say, on the other hand, that universe has existed from eternity, I might say: in that case it makes no sense to speak of the cause of the universe. Why? Because causes precede their effects. If you say the universe has existed forever, consider then -- is there a time before forever? Of course not, that doesn't make any sense. So it equally makes no sense to speak of the cause of an eternal universe; that cause would have to exist before something that had no beginning! There is no such thing as a cause of an eternal universe. All right, even if we concede that point, we can still insist: there has to be some manner of explanation or reason for why the universe even exists, and why it is as it is, and not radically different from how it is in fact. Here again we might bring up another principle to dignify our curiosity. This time it is the Principle of Sufficient Reason. Basically this says that there is a sufficient reason or explanation for everything. This principle was formulated by the German philosopher Leibniz. He wrote: "There can be found no fact that is true or existent, or any true proposition, without there being a sufficient reason for its being so and not otherwise, although we cannot know these reasons in most cases." Everything has a reason for its existence, and for why it is as it is, and not otherwise.
The cosmological argument simply applies the Principle of Sufficient Reason to the very fact of the universe. So it allows us to ask: Why does something exist, rather than nothing? And the principle allows us to demand an answer. And the answer, the theist says, is: God created the universe. That is a sufficient reason for the existence and nature of the universe. But notice, if we want to get around the objection I started this third objection with, we can't say that this reason isn't a causal explanation. God's creation of the universe explains why the universe is here; but the act of creation did not precede the existence of the universe. After all, remember that God is supposed to be, on many accounts, timeless: so it would make sense to say that a spiritual act of creation is timeless as well.
At this point you might be scratching your head in puzzlement. What exactly are we talking about in talking about a timeless, spiritual act of creation, which explains the universe, but which is not a causal act? Is there anything in our experience at all like this sort of "timeless explanation"? Well what about laws of nature? Force equals mass times acceleration, and so forth. Laws of nature are timeless; or, alternatively, they apply at all times, not just at particular times. And of course we can use laws of nature to explain things. So natural laws are one kind of timeless explanation we are familiar with. We can say: physical objects move the way they do because the laws that one studies in physics apply to those objects. Similarly biology studies the laws that explain the growth and behavior of living beings. Ultimately, a perfect, complete science would explain a lot about the universe.
But a complete science couldn't explain why particular bodies have been arranged in the particular way they have been; it couldn't explain why there was something rather than nothing; and it couldn't explain those laws of nature themselves. So we need God to explain those things.
Now, again, just as we raised objections to the Principle of Causality, we might just as well raise objections to the Principles of Sufficient Explanation. Why think it is correct? Why not simply think, for example, that the arrangement of matter in the universe simply is as it is? Maybe it is, as philosophers say, a "brute fact." Similarly with the laws of nature governing that matter: once you get to the broadest laws, that apply to the greatest number of things in the universe; once you have come up with some grand unified theory of everything; then there is no further question to be raised, as to why the laws of nature are as they are. Natural laws simply are, and there is no why. Well, that's what some people say anyway. I will leave it to you to think about all this.
Fourth objection. If we accept the cosmological argument, as we have seen, then we have to accept either the Principle of Causality, or the Principle of Sufficient Reason. All right, but then why not apply such principles to God? Consistency would seem to require us to do so. In other words, why not think that God's existence requires some cause, or at least some sufficient reason? Even a little child can understand this point. A little girl asks: "Why does everything exist?" Her mother replies: "God created it all." And then the little girl asks: "But what created God?" In other words, to say that God created the universe doesn't put an end to the little girl's curiosity. Her mommy might say, "God creates himself."
But now mommy's being a little disingenuous. If she means that God causes his own existence, then she is saying something absurd: since a cause must precede its effect, and the effect in this case would be God's coming-into-existence, God would have to exist before he came into existence; which is a contradiction. The point is that, if God either exists at all times, or timelessly, then in either case God never comes into being. So God isn't the sort of thing that can be caused to come into existence. Because God never does "come into existence."
But maybe we could say that, in some sense, God is a sufficient reason for his own existence. Be careful now -- I?m not saying that God causes himself. I?m saying that God's existence is a sufficient explanation of his own existence. But here, really, we might wonder: what exactly is the claim here? That something can explain its own existence, but not causally? This is straining our powers of understanding -- at least it strains my powers of understanding. Maybe there is a way to make sense of what it means to say that something could explain its own existence. But I can't tell you what it is.
So finally suppose, instead of saying that God explains himself, we say that God is the sort of thing that needs no cause or explanation or reason. God exists, as some philosophers like to say, necessarily. In other words, God is the sort of thing that must exist; it is a contradiction to suppose that God does not exist. If God exists necessarily, then there is no need to apply the Principle of Causality or the Principle of Sufficient Reason to him; since God must exist, he isn't the sort of thing that can be caused, or that requires any explanation. So the claim is: God's existence requires no cause or explanation.
Here's how one might reply to that. There are two ways to reply. First, I might maintain that there are no exceptions to the principles. After all, I?m not sure why it is that the fact, if it is a fact, that God necessarily exists is supposed to make it any less pressing for us to explain God's existence. Indeed, now we get to ask another question, namely, why is it that God doesn't merely exist, but that he necessarily exists? Do you see the point? If God must exist, then why don't we have to explain why he must exist?
Second, I might say: why not think that the universe exists necessarily? Why not think that the sum total of everything that exists, must exist, and must be as it is and not otherwise? In that case, then the universe's existence requires no cause or explanation, and we don't have to talk about God at all. Since the cosmos has to exist, we don't have to go around looking for explanations of its existence, or the natural laws that govern it.
I think you can see that, all together, these different replies to the cosmological argument make it difficult for the argument's defender to hold onto it. I'm not saying that that can't be done, because some religious philosophers have indeed used this argument and come up with elaborate replies to the objections I've raised.