It depends on what the "thing" is. For instance, houses are caused to be (are instantiated) by the humans that build them. Apples are caused to be (are instantiated) by the biological processes of apple trees (gah, I'm ignorant, but I think you know what I mean). Laws are caused to be (are instantiated) by the proclamations of legitimate authorities and the acceptance of the relevant communities. I don't think there is some single cause that all of these things have in common.

I think I've said this before, but I think you are intending to ask a question about the ontology of objects--something like: what is the difference between an object existing and not existing--but you put it in terms of causation, which seems to me a different issue.

For instance, I would say that the "essence" of water is H2O. Water is instantiated whenever the physical world combines in such a way that hydrogen and water molecules bond to form H2O. For instance, a chemist in the lab can artificially create water--in which case we would say that she started a process which caused water to exist. However, the fact that this particular piece of water was created by a chemist in her lab is an accidental feature of the water (and obviously of the essence of water more generally).

As for Aquinas's view of existence, I'll partially agree with Hume and Kant--I don't think that existence is a predicate (or at least, not an ordinary one--I think it is best understood as a second-level predicate). So I guess I would reject the way that Aquinas distinguishes between essence and existence.

You don't have to make a choice (in fact I don't think you can). Plenty would say they do not believe in the Christian God and also do not believe that everything came from nothing. Most of the atheists here don't know whether God exists and don't know if the universe spontaneously arose from nothing. They don't believe there definitely is a God they don't believe there definitely isn't.

You need to understand the position they find themselves in:

They've looked at the arguments put forth for christianity.
They've examined their experiences looking for something which self-authenticates.
Most of them have read the bible, although probably not in its entirety and they may well have found it either implausible or immoral from the get-go (I don't know many who claim to have read the whole thing before forming a judgement).
They've perhaps even been to church and 'tried' to believe as their faith faded.
They still don't believe in God.

What are they supposed to do? They can't just snap their fingers and decide to believe - can you change your belief by dint of will? Try and believe the sky is green for a moment or (to be a closer analogy) try and believe there are an odd number of stars in the sky (there might be, right? Try and view that as certainly true). Atheists aren't (usually) atheists by choice - they've looked at the world and see no reason to believe in God.

Analysing their position as if they see the world the way you do, yet declare they don't believe in God will always result in a nonsensical position - just as if they analyse your position from their perspective it will seem nonsensical to them.

its all BS of course because many of us asked God into our hearts, prayed to God regularly, never felt anything remotely like what Craig described. Heck, if we did many of us probably wouldn't be atheists.

He has an approach that I've seen many theists try here. If you don't believe its your fault because you prefer darkness.

Also, as usual, you can take all his arguments, replace it with the god of any other faith and nothing changes.

That's fine and I'm not suggesting you shouldn't. I guess I'm just drawing a distinction between your rejection of Thomistic metaphysics and when someone claims they've refuted it. Like when Hume redefines the Thomist's terms and then claims he's refuted their argument(s).

Strange as it may seem, there are those of us who are unable to choose to believe that any old thing is true just because we would like it to be true, or because if we don't believe it and then it turns out to be true we'll be in trouble. We require an actual likelihood that a thing is true before we are able to believe that it is true.

So do we.

I would describe this differently. I think Hume "refuted" Aquinas by redefining his terms. Hume (and some of his contemporaries) developed their metaphysical and epistemological theories as an outgrowth of the scientific revolution (and also some of the theological innovations sparked by the Reformation) and so their understanding of basic metaphysical categories tends to be modeled on the methods and categories of science. And since the acceptance of the authority and efficacy of science is one of the pillars of the modern mind, it is Hume's understanding of basic metaphysical terms like "being" that tends to be more appealing to modern sensibilities.

The issue I have with that approach is it delimits our definition of reality to what our metaphysical schemas can explain. That issue becomes a problem, for me, when questions that are deemed unanswerable are declared unaskable. I think Hume framed the issue/problem nicely when responding to the question, "… which determined Something to exist rather than Nothing, and bestowed being on a particular possibility, exclusive of the rest?" he says:

"But further, why may not the material universe be the necessarily existent Being, according to this pretended explication of necessity? We dare not affirm that we know all the qualities of matter; and for aught we can determine, it may contain some qualities, which, were they known, would make its non-existence appear as great a contradiction as that twice two is five."

So he's basically saying that even if we don't accept the major thrust of his argument and deem a necessary cause (existence) as necessary, we needn't conclude that necessary cause is God. Because for all we know, we may eventually discover an unknown quality of matter that renders the material universe it's own first cause.

I can't disagree that it's possible science will discover such a quality of matter or provide a natural explanation for why something exists rather than nothing. Nor would I suggest that science accept the metaphysics of theology and cease looking for a first cause, for then science would stop being science. Where I take issue is how metaphysics fits in the schema of philosophy.

With epistemology, we need to start somewhere, so if you want to start with 'existenents exist' I won't argue. It's when metaphysics is brought under the umbrella of epistemology; when reality becomes not what it is but what we can say/know it is that I seem to differ with the modern mind. I mean, I understand the necessity of doing so to further refine philosophical discourse but when I have logical grounds for asking a question that your metaphysics can't answer, your response is a rejection of my metaphysics, not a refutation. To clarify: from my metaphysical position, your response is a rejection, not a refutation; from your metaphysical position, you've refuted my metaphysics or Thomism.

To a limited extent, or for purposes of dialogue, I can incorporate your metaphysics into mine, but I don't see how you could reconcile yours with mine. The core of Thomism is the metaphysical position of being ultimately rooted in esse (act of being) and honestly, I don't see how that position could possibly fit with analytical metaphysics. Theology, or the God question, will always be 'unknowable knowledge,' so I'm fairly certain where we'll part ways.

If you take a look at Geisler/Zukeran's The Apologetic of Jesus you'll see them refute Hume. Iirc they showed the flaws in his assumptions on some of his proofs.