I’ve thought about the commonly used Christian philosophical arguments for the existence of God, and I think that there is something most Christian apologists are missing in their logic that I would like to point out.
Firstly, I’d like to talk about the Cosmological Argument.
This is an argument based on logical and scientific inferences from our observations on nature. It is true that nothing which begins to exist caused its own existence, for this is a illogical. Also, I’d like to point out that it is impossible, or at the very least logically unsatisfying, to assume an infinite regress in the chain of causality in the physical plane of matter/space/time. Whether or not a quantum shift, or God, or what have you, is the cause behind the big bang/creation of our universe, it is at the moment unimportant.
The most you can logically deduce from the cosmological argument is this, so far as I can tell.
That our universe plainly began to exist at a finite time ago, before which space/time/matter did not exist. This is evident from the big bang, and from the necessity of the illogicality of infinite regressions. Even if you think that maybe there was a big crunch/big bang circling into infinity, this would still constitute a necessarily illogical position due to this simply still being an infinite regression with no end or logically necessary beginning, and this is true for multiple universe theories as well. So really whether or not big bangs/crunches are part of the natural order, those too must necessarily begin at a finite amount of events ago in the past, otherwise the concept of infinity would leave those events without ever reaching the present. In fact I might go so far as to postulate (just my own idea) that infinity is impossibly in the physical world. Thus at the very least we can postulate that the most reasonable position to conclude from logical and scientific evidence is that our universe began at a finite amount of events ago.
Since it is illogical, or at the very least scientifically and logically unsatisfying to postulate that nothing caused our universe to begin, we can conclude that something caused the universe to begin. Ultimately this is as far as the cosmological argument will allow us to go.
I feel like Christians take a logical jump at this point, and this is where I feel this argument will fail in their favor. At best, I believe all you can conclude is that it is the most reasonable position to hold our universe began and had a cause to its beginning. Logic and philosophy can only take us this far. To jump from that to say “so clearly God caused the universe” makes a logical and philosophical jump without merit.
Simply from the logic and science, one can only conclude that there must necessarily be a cause, but at the very best all we can say about that cause is that we simply do not and can not, by light of science and reason/logic/philosophy alone, know what that cause is.
Thus the most reasonable position you can hold based on this logic is one of agnosticism. I feel like this is in fact a good starting point for Christian apologetics since you could go on from here to show why you feel the belief in the Christian concept of God is the most reasonable belief about what the unknown cause is, but I feel it is dishonest logically speaking to jump immediately from the position of logically reasonable agnosticism to Christianity. That is all.