granpa said:
we may ask what the first cause was but we can't ask what caused it.
Who said there had to be a 'first cause'?
'First cause' is a contradiction to Newton's third law. If there is an effect - big bang, there must be a cause. And there must have been a cause to cause the big bang, and so forth. It is an unending question of why's, the only conclusions are that this reasoning is false, or there is no 'beginning' and therefore an infinite string of causes.
This law is the basis for all our logic - or our logic is the basis for this law - either way, it is our only way of understanding things - which is in terms of 'cause and effect'.
If A, then B... if B, then C... and if B, then we can say C will occur, and that A must have preceded B if nothing else causes B.
Either this logic holds infinitely and there is no beginning, or our logic is flawed.
'Since the universe exists, it must have been created, and something must have caused that to create it...' - to deny this question is to deny any other question based on the logic of cause and effect.
There simply cannot be special cases in this logic. It is either true, or it is not. There are no exceptions.
Your pizza scenario is irrelevant. Clearly, those are two independent things. However, the creation of the universe and the cause of that cause are not independent - by definition one effects the other.
I would say more about a theory which supports the big bang and evidence for it, but argues it is not the 'creation', but that is for a different thread.