Part 2 of this series I talked about Thomas Aquinas' "five proofs" for the existence of God. There are a couple of things to add before we go onto other arguments. In the last post, Einstein, Hubble, and Lemaître demolished Fre Hoyle's steady state model of the universe, but there are two other logical replies to the "uncaused cause" argument that are commonly given to avoid a universe with a beginning.
MultiverseThe multiverse hypothesis holds that the universe exists because all things that can exist exist, everything that can happen happens. This not only appears to get around the origin of the universe, but of any need for any sort of deity, belief, moral stricture, etc. Everything is random. There are a couple of problems with this, both logically and scientifically. First off, the logician might say "OK, why does everything happen, rather than nothing" which is really Thomas' "why is there something rather than nothing" question repackaged. You still have to posit and uncaused cause, only now it's for everything, not just the universe.
Secondly, if everything that can happen happens, why doesn't it happen in our universe? Why don't the laws of physics suddenly change? Why doesn't the laptop I'm writing on turn into a grapefruit? How can we ever believe in a scientific principle, when those principles can change at any given time?
"Oh, but Mike, they can't!" you reply. Why not? Show me, if everything that can happen happens, how you can ever posit that something can't happen in this universe. Perhaps this is the universe where gravity reverses every 13.7 billion years, which happens to be tomorrow? If you believe in an ordered universe, then you have to suppose that not everything that can happen happens, and if you're going to put some restrictions on it, occam's razor would suggest that rather than limiting it to only those universes you like, using a large number of restrictions, you might as well go the whole way and say there's only the one, and it's the one we're in and this is how it works.
Besides, evidentially we can only say there is one universe, despite attempts y some to wish that every bit of unexplained data "leaks" in from another universe. Once again occam's razor suggests an argument from evidence is stronger than one based on wishing.
Bouncing UniverseThe second argument against the beginning of the universe is the "cyclical universe" or "bouncing universe" hypothesis. This is the one Stephen Hawkings resorts to in his latest book. In this we suppose that the universe either repeats itself forever, or changes each time (which is basically a serialized version of the multiverse). Either way, there are still two flaws with this hypothesis. First off, in the sense that this is a serialized multiverse, it is subject to all the counterarguments above. Secondly, the second law of thermodynamics makes it impossible. Like a ball that bounces a bit lower each time, our bouncing universe is subject to entropy and will run down.
In fact, what Hawking conveniently left out of his book were all the scientific arguments against the bouncing universe. One of these is the Borde-Vilenkin-Guth Theorem (BVG). In 2003 Borde Vilenkin and Guth came up with a proof that says that given the laws of physics, any universe or system of universes (whether they be bouncing or multiverses) where the universe has a Hubble expansion rate greater than 0, must have a beginning.
In fact, this proof is vastly applicable to just about any model universe or multiverse that could be produce our universe. Alexander Vilenkin put it this way in 2006:
We made no assumptions about the material content of the universe. We did not even assume that gravity is described by Einstein’s equations. So, if Einstein’s gravity requires some modification, our conclusion will still hold. The only assumption that we made was that the expansion rate of the universe never gets below some nonzero value, no matter how small. This assumption should certainly be satisfied in the inflating false vacuum. The conclusion is that past-eternal inflation without a beginning is impossible.
Kind of hard to hold to eliminate a "first cause" at this point, no?
I think this puts the last nail in the coffin for the arguments against Thomas' five proofs (or at least all the ones I know - do you know any others?). I realize that at this point all I have addressed is "does the universe have a creator". I have not shown that that creator is an "invisible friend in the sky" or even that the creator is an intelligence, only that a creator exists. It's going to take a long time to get to that.
In the meantime, I would like to highly recommend Robert Spitzer's book New Proofs for the Existence of God: Contributions of Contemporary Physics and Philosophy. The physics section will give and awful lot to chew on, such as the above.