Tim Wood, thanks again for a good analysis. It makes me happy to see people seriously thinking about the issue. Your main issue is with the idea of cause, and first cause. Fantastic. I have not had a good discussion on this. SophistiCat, I hope my analysis below will always clarify what I mean, so feel free to contribute your own thoughts on this.
Let us think of slices of time as "states". At its most simple, we would have a snapshot. But we could also have states that are seconds, hours, days, years, etc. We determine the scale. Within a state, we analyze the existence that has occurred. Causality is the actual prior state, not potential prior state, that existed which actually lead to the current state we are evaluating.
If a state is of a larger scale than a snapshot, then we can subdivide this state. So let us say that I have a state that is two seconds long. I subdivide it into seconds. The first second is the cause of the second. It is not that the second "second" could have have existed without the full first second of time. We might state that in reality, only the last millisecond of existence within the first second, was needed to get the second second of existence. We then might say there were potential states of existence prior to that millisecond, that could have lead to that millisecond, that then lead to that second second.
But in the end, potential is not actual. The actual is what actually happened prior to that millisecond. Despite our idea that we only needed the last millisecond of the first second to have the existence of the second second come into being, the full actual chain of causality in milliseconds is the full first second.
So then what is a first cause? A first cause is when we reach on our scaled state, a state which has no actual prior state. If our scale is in seconds, there is no prior second. If a snapshot, there is no prior snapshot. We can imagine there are prior states. We can float possibilities. But as an actual existence, there is no prior state.
If there is no prior state, then there is no reason for the first state that is, to have existed. For the reason of a current state, is explained by the actual prior state. All we can say as to why a first state existed, is that it did.
So what I do here in determining the logical necessity of a first cause, is examine the entire state of the universe. We know what a finite state universe looks like now, but what about an infinitely regressive stated universe? At this point we are not positing actuals, but potentials. We are trying to see if a first cause is a potential, a contradiction, or a necessity.
When examining the potential of an infinitely regressive universe, if we subdivide it into its finite parts, there of course is no end. Just like I can divide seconds into milliseconds and so on, so can we divide the infinite into whatever scale we want. But we can also do the reverse. Just like I can make a snapshot as the state, I can make the state the sum total of the time of the universe's existence. I can look at the two second universe in the scale of "A universe", That is universe A. I can look at the infinitely regressive state universe and make the scale of "A universe", and call it universe B.
Once this is done I can ask a question. Is there an actual prior state that happened which caused universe A? No. So there is no causality for its existence. I ask the same question about universe B. Is there an actual prior state that happened which caused universe B? No. So there is no causality for its existence. The only thing I can logically conclude from the above premises, is that there is no cause for the existence of any potential universe. Whatever universe exists, exists without prior explanation.
Lets examine this thought process before I move on. Does this clarify my position? Any holes, any questions? It is nice to dive deep like this.