I note the equation of atheism and science but make no further comment :-)
>The book's defense of this sense of free will, where God is free to choose not to cause the universe, is simply that "the freedom of the divine will is mysterious to us", which I think you'll agree is not any sort of proof.
Feser is not offering this as proof of the existence of God's free will. He's answering a particular objection: how is it that an unchanging Being can will, given that we, as changing beings, necessarily change from willing to not-willing and back again? He says that using this as a ground against God's having will is to commit the fallacy of accident. And then he's saying we can't understand the full details of how God can will without changing, but that we can nonetheless safely say what is not the case: that God lacks will. (My summary of his argument is below.) Therefore I think your characterization of his argument is inaccurate.
If either A xor B is true, and we can show that A is false, we know that B is true. Perhaps there are implications of B that are impossible to grasp even in theory, but this doesn't undermine the truth of B. Agree?
One way we know that God wills freely is by comparing a lion, a unicorn and a dinosaur (I'm paraphrasing the argument on Will in Chapter 6 here). There is nothing about the concept of a lion that causes it to exist, there's nothing about the concept of a unicorn that causes it not to exist, and there's nothing about the concept of a dinosaur that caused it to exist at one time but then caused it to stop existing. On the contrary: I could describe the concepts of a lion, a unicorn and a dinosaur in infinite detail, and you wouldn't know from what I had told you which is real, which is historical and which is imaginary.
What I said about those three animals is true about everything. You could describe the concept of anything in infinite detail without knowing whether that thing exists or existed. There is nothing about a lion as such that makes it real, and nothing about a unicorn as such that makes it imaginary. There is nothing about a lion that makes its existence necessary, and nothing about a unicorn that makes its non-existence necessary. The existence or non-existence is a completely separate question from what it is (its qualities, etc).
Now consider the principal of proportionate causality (described in the book in detail). This basically says that if a thing doesn't have a particular quality in itself, that quality must be caused by something else. Example: I can't lift myself 10000 feet into the air, but an aeroplane can cause me to 'have' this quality. A particular pool of water may be red; it is not the water itself that's red, so something else must be giving it this quality. Etc.
The result of this is that any object that exists must be caused by something else to exist, and that this 'something else' must exist in and of itself. (This is obviously contained in some of the proofs.) Obviously the proofs say that God is such a 'something else'. Therefore, God is causing lions to exist, caused dinosaurs to exist at one point but no longer does, and has never caused unicorns to exist.
But we know that there is nothing in lions that makes them exist, nothing in unicorns that makes them not-exist, and nothing in dinosaurs that makes them stopped-existing. So, assuming the claim that God causes their existence from moment to moment succeeds, if follows that their existence or non-existence is a matter of choice. The fact that He is causing one to exist and not the other two indicates that He is choosing to do this. Given that there is nothing in any of the three that causes it to necessarily exist, it follows that the real things we see are not some sort of 'natural bursting forth' from an impersonal being, but rather exist by the choice of this Being. If the universe 'burst forth' from God, then anything that could potentially exist, would exist.
>> God cannot possibly lack anything ... It would be impossible to cause something that you don't in some sense have yourself
> base qualities and emergent qualities...But that does not mean iGod itself can be attributed the quality of being an atom or a galaxy or a human body. Causing some quality to exist down the causal chain does not mean it is meaningful to port those qualities back up the chain.
I disagree with the reductionist account of a table that is I think implicit here -- I think tables (or at least the wood that constitutes the tables) are metaphysically prior to the atoms that compose them, and the same for all natural objects. By this, I mean that the parts can only be understood in terms of the whole, and must be understood as subordinate to the whole, not vice-versa. But if I understand your objection correctly, I think I can work through it even allowing for the reductionist ontology. The principle of proportionate causality illustrates things well. Could you read the book's account of this principle? It's early in Chapter 6, I think pretty much the first section. I think you're using the 'heirloom principle' to object, which assumes that the Principle says that an effect must exist formally in its cause, and ignores that it can also exist eminently or virtually. The book defines these terms, and attempts to explain why the objection is not valid. Do you think the attempt succeeds?
If you think the attempt succeeds, I will go on to discuss why, given some things in reality (human beings) have a will, it follows that that which causes human beings' existence must also have will, either in the same sense as human beings or in some greater sense.
I'll try to respond to your other post when I get a chance. Some of the points are fairly different from what we're discussing here. I'm happy to talk about whether God revealed Himself, and in what sense he governs our conduct (or has a right to do so), but it's a pretty different conversation.