Again, none of this is known for sure.
But I believe it can be shown that the KCA is more plausibly true than not, and that is the position of Craig. So far, the best objection I've heard on this thread is "We don't know". Not only has no one succeeded in showing that Vilenkin currently believes in an eternal universe (he used to, but not now), but no one has even addressed the rest of the support for p2:
1. The philosophical arguments against infinite regress.
2. The 2nd law of thermodynamics suggests that if time was infinite, then the universe surely would have fully expended all of it's usable energy by now.
3. Einstein's Theory of General Relativity suggests a beginning of the universe. He originally tried to create a "fudge factor" to avoid that conclusion but later had to retract it and called it the biggest blunder of his life.
4. The discovery of the red-shift suggest the expansion of the universe and implies a beginning.
5. The discovery of the background radiation also matched the level of what was predicted by earlier theories.
And also, as I said once before, this universe might now be the only one.
Yes, and I replied that the BGV theorem suggests that even multi-verses had a beginning.
So again, I believe there is good evidence and argument to show that p2 is more plausibly true than not.
All I'm trying to say is that humanity has a lot to learn still, we've come a long way, but we have a much longer way to go. And there are a lot of things we have ideas for, but for me personally and any other scientific thinker and/or scientist, like Sean Carroll said in the quote in the reply above, we are willing to admit that we don't really know.
I'm a "scientific thinker" also. I took several physics courses (up to and including General Relativity and Quantum Mechanics) and read numerous books on the subject. But I don't think that proves anything anyway. There are also numerous scientists who believe that the universe had a definite beginning, most notably Stephen Hawking. He developed a theory that avoided a singularity by inserting what he called "imaginary time". He explained that doing this allowed him to perform certain complicated calculations. But he admits that Imaginary time is just that...imaginary. It's just a mathematical contrivance.
"Only if we could picture the universe in terms of imaginary time would there be no singularities...When one goes back to the real time in which we live, however, there will still appear to be singularities." Hawking in
Brief History of Time page 138-139.
It really boggles me that your won't even at least meet me half way with that one.
I even said, that there is a possibility there could be a god, but you won't even say there is a possibility that there could not be. That's the difference between you and me, I'm open to everything, some things I find highly unlikely, some things I don't, but you think one thing is very likely and shut out any other possibility.
The reason I cannot agree that there is a possibility that God does not exist is because I have the witness of the Holy Spirit. I know that means nothing to you. That's a different subject though, and I'd rather stay on the KCA in this thread.