This argument is set up as a syllogism. A syllogism is a set of premises which, if true, always prove that the conclusion is true. Craig's syllogism is as follows:
- Whatever begins to exist has a cause.
- The universe began to exist.
- Therefore, the universe must have a cause.
1: Whatever begins to exist has a cause.
This premise is empirically verified wherever you go. We just don't see things popping into existence left and right without causes. You don't expect to be sitting in your dorm room and suddenly see a centaur on your roommate's bed. Our day-to-day experience overwhelmingly supports this premise.
There are two main objections to this premise. The first is based on quantum mechanics. According to some views, subatomic particles can come into existence uncaused from the quantum vacuum and disappear after a brief period of time. However, not all physicists believe that the source of these subatomic particles is indeterminate - that is, not all believe that they are uncaused. David Bohm suggests a model wherein the cause of these particles is unknown, but not nonexistent. This model is just as consistent with the math and evidence as the more common Copenhagen interpretation proposed by Niels Bohr. Bohr's view maintains that these particles arise spontaneously from the quantum vacuum and seem to be uncaused. However, even this view doesn't account for something coming ex nihilo - out of nothing. The quantum vacuum is not nothingness, it's a sea of fluctuating energy.
The second objection is based on Ockham's razor. According to Ockham's razor you should not multiply causes beyond necessity, it argues that the simplest explanation is best. This objection also falls short. Ockham's razor says not to multiply causes beyond necessity. It does not allow you to eliminate the necessity of causes.
Objections from quantum mechanics fall short for two reasons: alternative, equally valid interpretations of the origins of subatomic particles do not propose that they are uncaused, and even if they were uncaused they would not be coming into being ex nihilo as the universe did. The objection from Ockham's razor fails because of a misunderstanding of Ockham's razor. Premise (1) stands unrefuted. We will now move on to premise (2).
2: The universe began to exist.
We will look at this premise both philosophically and scientifically. The philosophical support deals with infinites. First of all, an actual infinite - such as an infinite regress of events (a series of events extending forever backward) - cannot exist. An actual infinite is a collection of somethings that is already actually infinite. In contrast, a potential infinite can be something that grows toward infinity, but has not reached it (and in actuality it never will, as I will address in a moment). Another problem with proposing an infinite regress of events is that you can never reach infinity by adding. You can always add more, so you will never have reached infinity.
Scientifically, there have been two main theories that suggest alternatives to a definite beginning of the universe: the steady-state universe theory, and the oscillating universe theory. Both fail to address the problems I addressed above, but they have also been disproven scientifically. The steady-state theory, as the name implies, states that the universe has always been and always will be just as it is. This has been disproven in a number of ways, but for now we will address one reason. Astronomers have observed what they call the red shift. The red shift is a reddish tint to other stars and galaxies that implies that they are moving away from us. From this we can reason that if we go back in time we can condense the universe to a single point.
To account for the universe's expansion while avoiding an absolute beginning to the universe, the idea of the oscillating universe became popular. This theory stated that the universe does expand, but at some point the expansion slows down, the universe collapses upon itself imperfectly, and out of this is begins to expand once more. There are all sorts of problems with this theory. First, a certain mass would be needed for the universe to slow its expansion and collapse upon itself, and the estimated mass of the universe is nowhere near as large as this number. Second, we have no reason to expect that a universe of the massive bulk needed to collapse would rebound and expand once more after collapsing. Furthermore, if it did rebound, some energy would be lost each time, and each time the re-expansion would be less powerful, leaving you with the problem that you would have to expect that as you recede through infinite implosions and explosions you observe an infinite increase in the amount of energy available.
The steady-state universe and the oscillating universe not only fail to address the philosophical issues, but they fail scientifically. Nearly all other proposed theories merely push back the origin of the universe rather than eliminating the problem. Based on the scientific evidence provided by the red shift and the philosophical reasoning regarding infinities, the only reasonable conclusion is that the universe did, in fact, begin to exist.
3: The universe has a cause.
The syllogism is valid. The conclusion follows logically from the premises. The premises are supported. This leaves us with very little room to deny the conclusion. Where can we go from here? As of right now, the cause could be anything. If I stopped here, it would be ridiculous to say that I have proven that the Judeo-Christian God exists. However, by looking at what the universe is, we can learn quite a lot about what its cause is not.
- It can't be constrained by or composed of what it created. This means that it is immaterial, non-spatial, not bound by time, and doesn't use any form of energy that we know of.
- It must be immensely powerful. Creation ex nihilo isn't exactly an easy task.
- It must be a necessary being. This means that all things depend on it to exist, but it depends on nothing to exist. This implies that the first cause was uncaused. Note that this does not violate (1) from the syllogism because this cause is not bound by matter, time, etc.
- It must be a will-based being. The only other option is for it to be a mechanism that creates any universe that has a non-zero probability of existing. This means that any conceivable universe would have to exist, but we have no reason to believe that this is the case.
