1) Consider the principle that there is some explanation for everything that happens or exists. This idea seems compelling. Scientists and historians examine the world believing that there are explanations for the facts they discover; they do not do so in vain. But if laws of nature, billions of fundamental particles, relativistic quantum fields – if entire universes, in effect – can exist without explanation, why should we assume that there are explanations for everything that happens in the universe? Why not give up when we fail to find explanations for something mysterious. There is good reason to accept the principle, whereas denying it seems to lead to scepticism. So we need to provide an explanation for the existence and order of our universe.
2) Now some speculative physicists have tried to demonstrate that the universe could come to exist out of nothing. We should note that they have conceded that we should not treat the existence of the universe as a brute fact, in no need of further explanation. We should also note that “nothing” always turns out to be “something”. These accounts always make use of laws of nature and state spaces. By “nothing” they mean “nothing-like-the-space-time-universe-which-we-currently-observe”.
But in metaphysics, and indeed, in ordinary language, “nothing” typically means “nothing- at -all!” No laws, no energy, no potential, no activity; this is why we find it so difficult to imagine “nothing”. We immediately think of a black, empty space. In which case, of course, we are imagining something. We are imagining a space and darkness. But nothing actually means “non-being”; there isn’t anything to imagine. It cannot be described by the laws of physics. There is nothing to describe!
3) Perhaps we could argue that each state of the universe is explained by the state just prior to that. If scientists explain, one by one, all the physical reactions and transformations that have taken place within the universe won’t they explain why the whole universe exists? And suppose the universe is infinitely old. Each state of the universe will then have a full explanation. Won’t we have an explanation for the existence of the universe at that point?
Unfortunately, this does not seem to be the case. By explaining each physical transformation and reaction in the universe we don’t answer the question “why can transformations or reactions happen at all?” Even if there are infinitely many events, we are still left with questions – “where did this infinitely long series of events come from? Why does it involve these laws and not others? Why is any of this happening?”
4) If the universe cannot explain itself, we need to identify an explanation external to the universe. God seems to be a good candidate. Physical beings have limitations by nature – the physical universe is limited by time and space and energy. God simply is unlimited intentional power – or less technically, unlimited power and love. If there is a God he would have to transcend the limitations of the physical universe. No force or state of affairs could prevent God’s existence. Here is the key point: unlike the universe, God is explained by his own nature. If there is a God, no matter what else is true, God must exist. It would be impossible for God not to exist! God’s existence would need no further explanation.
5) If that seems too abstract and metaphysical, consider this principle: we should push our explorations as far as possible; we should try to understand as much as we possibly can. Now, the theist and the atheist both accept that there is something that is not explained by reference to anything external to itself: God in the case of the theist and the universe in the case of the atheist. This raises the question as to the most suitable terminating point for explanation; is it with the universe itself or with God?
It seems reasonable to make God the stopping point. Our universe gives the overwhelming impression of design. We see incredible order in the living world, the subatomic world and in the structure of the cosmos. Now why should the universe display this sort of order? Physics cannot give explanations in the absence of laws. It follows that physics cannot give explanations for the laws of physics; if we are to explain the laws of physics we must look for an explanation beyond physics.
6) So there cannot be a scientific explanation for the existence of the universe, because there can be no such explanation without laws of nature and the physical objects they describe. Yet that is exactly what we are trying to explain when we ask “why does the universe exist?” However, scientific explanations aren’t the only kind of explanation: there are also agent explanations.
7) Theism provides an agent explanation for our universe. It describes an agent, God, who has the power to bring the universe about. And God would have good reasons to bring an ordered universe about; it allows him to create things of beauty and wonder. If God exists, by definition, he could not be explained by anything outside himself. By contrast, it seems entirely possible that the universe could have a cause and hence an explanation. God could not have a beginning; whereas, it is at the very least possible that the universe has a beginning.
At this point we can give no further explanation; because God is unlimited in power, there is nothing outside God that could explain his existence. We cannot gain any more understanding in this area, so our enquiry is complete.