Thank you for detailed response.

> to summarize where we are at this point

I think it's a fair summary, yes. I hope you understand by now my views on the words "sustains" and "caused": (possibly) passive, not active.

> Whereas your position is that concepts are meaningless, or somehow like 'images' perhaps, or cardboard cut-outs, and perhaps only exist in human minds

Ah no. I'll try to clarify.

So what is our overall goal? We exist. We sense a universe. And we're trying to explain where we and this universe came from. By logic, there has to be some First Cause. But we don't know the properties of this First Cause directly. We can only observe the effects and try to surmise what First Cause can consistently explain all the effects we see. Makes sense? Now given our observations, there are multiple hypothesis that fit our observations. Personal God. Impersonal physical laws. Brain in a vat. Simulation in a matrix. Etc etc. I got pulled into this (fun) conversation because the book claimed that it can logically show that the First Cause has to be a personal God. And my attempt has been to show that the questions raised in the book can be explained by impersonal physical laws as well. I'm not saying that the First Cause is definitely impersonal. I'm only claiming that given our current observation as of today, impersonal physical laws can explain all of our observations and we don't need the personal God hypothesis to explain anything (logically). Only by including observations such as divine resurrection does a personal God make sense, but that is beyond the scope of the book (and hence I've tried to stay away from in this conversation, even though it does interest me to know your views on that aspect as well).

> I think the key difference is whether the concept of a unicorn or anti-gravity has existence independent of our minds.

Okay so regarding the concepts. I definitely agree that concepts exist outside human minds. That's what I mean by logical possibilities. Now I said that impersonal physical laws can explain the universe we see. Imagine instead that there was no universe. No First Cause. Nothing. And yet, all logical possibilities, including entirety of mathematics, would still "exist". So taking the physical laws of our universe as an axiom, the entire history of our universe would still logically exist (think of it as sort of a blueprint or wireframe), right? And in this ghost universe, lions will "exist" and unicorns won't. Do you see what I mean? The concept of a lion is not contingent on actual instantiation, but definitely needs the logical axioms of a universe.

> > If I point at a particular lion and say "what makes it a lion?, what do you say?"

To take another example, it is hard to imagine what the concept of a triangle would mean without first assuming the axioms of geometry, including points and straight lines. Triangles depends on those base concepts and exist in this larger world of geometry. Similarly, I'm saying to explain "what makes it a lion?", it is both necessary and sufficient to state the physical laws + initial conditions of our universe, not instantiated but logically. And as soon as we state the axioms, the corresponding ghost universe will naturally contain in it life and evolution and lions by logical implication. In this sense, lions exist outside human minds, not independently, but as part of this larger logical universe. God may be needed to give concrete life to the axioms, but the rest can be just a natural outcome without separately needing God to cause each thing individually.

> some explanation is needed as to why the concept of a unicorn lacks existence as a concrete object but the concept of a lion has existence as a concrete object.

Now of course there are many many possible logical universes: Our exact universe. Our universe but anti-gravity. Our universe but unicorns popping into existence 14 billion years after a big bang. Our universe but with a personal God. All logically valid possibilities. I think this covers what you mean by physical laws being contingent. And the question is, which among these universes do we actually live, given our observations. And logically, it is possible (and as a naturalist is obviously more likely to me) that we live in a universe which started with one set of rules (the First Cause) which instantiates the ghost universe implied by those rules into a concrete reality. This is what I mean by "bursting forth". The eternal immaterial First Cause in my version is just a one set of rules (out of many possibilities), from which the universe as we see it emerges as naturally as all the patterns of a Game of Life emerges from its rules. Whether this is actually reflects the true reality or not is up for discussion, but this fits our current data, and hence disproves the exclusive theistic conclusion of the book, which is all I'm trying to establish in this conversation.

> Hydrogen has an actual (not potential) property of being burnable.
> It isn't actually wet (like water) or potentially wet.

Sorry I was being sloppy with my words here.

> Do you agree that hydrogen and oxygen lose all their properties when they become part of water, due to the bond they form? Am I being fair when I say this implies that the substances themselves cease to exist as complete entities, and continue to exist only as part of something else that is now itself the complete entity?

This is again a case where I seem to agree with the sentence but our takeaways are very different, possibly because we're attaching different meanings to the words "lose all their properties" and "cease to exist". And I'll refer again to the concept of (weak) emergence to explain how I think about these things. All there is in reality is a set of base rules, which are the physical laws that govern this universe and gives properties to base entities (whatever they are). Of course we don't know the full story yet. But whatever we know so far: quantum mechanics (fields) + general relativity (spacetime), that emerge out of the base rules, gives a huge explanatory power to our ability to understand and predict how the universe works.

It is also important to realize that in our everyday conversation, we heavily use multi-level abstractions. To reuse an example I read, say my partner asks, why is there a pizza delivery at our door (and say it is), there are many possible answers. Because I ordered pizza. Because I was hungry. Because we live in a capitalistic society which allows things like pizza delivery. We can keep asking why, and will ultimately end up with a base reason: Because of the physical laws and initial conditions of the universe (or because God willed it so). So which is the correct answer? All of them. At different levels of abstractions. Hence, emergence. And of course, we have to use the right abstraction when answering questions. Saying the initial conditions of the universe as an answer to there is pizza might be okay as a geeky joke at a physics conference, but will probably only lead to an unhappy partner if used as an answer at home :)

So back to the hydrogen example. All that exists are the base rule. H/O/H2O do not "exist" in the base rules. Instead, they are emergent out of the base rules at some level of abstraction. H itself consists of protons and electrons, with protons made up by quarks etc. So when H combines with O to form H2O, think about what happens to the electrons and protons in the H and O. Do they change in any sense? No. They keep being electrons and protons. So what changed? Only the emergent properties of a group of H and O. And only at the level of everyday human experience. When we look at the H inside water and the H in a hydrogen tank, we will still find electron and protons behaving in the exact same way. So nothing has changed there. What has changed is what is in the vicinity of H. When there are only other H in the vicinity of H and O2, it has the property of being able to burn. Why? Because it has a free electron that gives H the property of being able to attract an O. But once it has succeeded on attracting an O, and thus is in the vicinity of O (not O2), the property to burn has "ceased to exist". But only in the sense that it is latent due to the presence of O. H still is a complete entity and O still is a complete entity, but in the presence of each other, some properties become latent. And sometimes electrons can actually completely cease to exist, say by colliding with a positron and turning into photons. But even here, what matters is that all these interactions are consistent according to the base rules, say of conservation laws. This is the beauty of emergence.

Now I also realize that your critique is of "reductionism". I am not particularly attached to this word if that helps. I only aim to explain why I think that the God the proofs are trying to show is only needed at the edge of the hierarchical chain. We may need God to explain how the universe started. But once it got going, physical laws can (and do) completely explain the rest. We don't need God to separately explain lions and hydrogen and gravity. Consider the idea from the book of me giving $20 to Alice. So sure, I caused Alice to have $20. Now say Alice, unknown to me, gives the $20 to Bob. Thus I caused Bob to have $20. But only indirectly. I didn't even know Bob existed. Similarly God sustains the physical laws and the physical laws sustains the next level and so on, until lions emerge out of the linear/hierarchical causal chain.

[0] https://youtu.be/6avJHaC3C2U?t=297, highly recommended video