The KCA:
1) Whatever begins to exist has a cause.
2) The universe began to exist.
3) Therefore, the universe has a cause.
So far, I haven't seen a single good objection to the second premise. And I think most people are on board here - the universe began to exist a finite amount time ago. It's the first premise that has been the bigger target here on DTF. I don't think it's an implausible premise, myself, but mostly because its only alternative ("Whatever begins to exist does
not have a cause") is absurd.
But there is one objection that's been raised which really gets me. and it's rooted in "mereological nihilism". That's the view that no individual 'thing' actually exist as things more than the materials that make it up; rather, they are material arrangement in the shape of those things. Because the human brain is evolutionarily trained to think macroscopically, humans have designated names for commonly encountered material arrangements in the human experience. These names are ultimately arbitrary categories. Thus, things like 'chairs', 'stars', and the concept of 'I' do not exist in reality as anything other than the arrangement of matter into the shape of those things.
On this view, nothing ever begins to exist. 'I' did not begin to exist at conception, when my first cell's 46 chromosomes got mashed together for the first time. 'I' have existed since the beginning of the universe, because the material that makes up 'me' has existed since the beginning of the universe. Therefore, the premise "Whatever begins to exist has a cause" has no ground in what we see in reality, because nothing has ever actually begun to exist.
tldr; just click the link v
https://en.wikipedia.org/wiki/Mereological_nihilism It's probably better at explaining this than me.
So...what do we think about this? If it's true, I believe it could destroy the KCA, as we are then simply speculating about Premise 1. But the KCA still
could be true, and I'm willing to buy Premise 1 because its opposite just doesn't make sense at all.
If it's false, then I think the KCA stands quite firmly where it's at.
One possible objection that came to mind as possible key to refuting MN is that if "only basic building blocks without parts" exist, then, well, you're led to the eventual conclusion that
nothing exists at all. You could chop matter in half an infinite number of times and show that everything is made of 'parts'. Even atoms, while not technically divisible, can be chopped up into the 'right half of the atom' and the 'left half of the atom', etc.
Of course, if the eventual conclusion 'nothing exists' is false, then one of the premises of MN is false. No idea which one, though.
Aaaaand..........we're open for debate.