Ed, I would like to respond to each question first before responding to your responses; otherwise things could get confusing.
Here is your second question:
2. Could you tell us where in your writings or in someone else’s that we can find what you take to be the strongest criticisms of the Scholastic arguments for the doctrine of divine conservation?
Good question. Actually, I think that recent atheist writers have been remiss in not addressing this question or Thomistic metaphysics in general nearly as much as they should. Nicholas Everitt does have an interesting discussion of the Cartesian conception of continuous creation on pp. 271-274 of his book The Non-existence of God. In general, however, recent atheist writers have focused on the more recent theistic arguments, such as those by Alvin Plantinga, Richard Swinburne, William Alston, William Lane Craig, J.P. Moreland, Robert M. Adams, Peter Van Inwagen, and others. This is too bad since Thomism remains a respectable tradition with many knowledgeable and articulate supporters. BTW, in teaching my history of philosophy class today, I still draw on Etienne Gilson’s little classic Reason and Revelation in the Middle Ages. Gilson’s writings were some of the most useful when I was studying theology and the history of philosophy at Emory University in the 1970’s.
My view of divine conservation is that it is rather plainly a gratuitous notion. Why would, say, an electron or a quark (considered fundamental particles in the Standard Model) need any help in remaining in existence? The idea seems very odd to me, like the idea of “vital force” to a modern biologist. We know that highly respectable biologists of the past, like Louis Pasteur, adhered to the doctrine of vital forces, but it eventually was discarded as non-explanatory. Similarly, I have to ask what explanatory work is done by the principle of divine conservation. What legitimate questions does it answer? Is there anything missing from an electron that would have to be filled in or supplied from outside?
There is nothing in our physical theories that indicates such a lack. Of course, there is the famous “measurement problem” of quantum mechanics. The dynamic properties of quanta have no specific value—but are represented as a superposition of possible values—prior to measurement. Still, whatever solution to the measurement problem we favor, I do take it that most scientific realists (like me) hold that quarks and electrons do objectively exist “out there” independently of us. As Ian Hacking notes, in many ways subatomic particles can be used and manipulated like other things. We can store them, shoot them, block them with barriers, and achieve all sorts of effects (some quite horrible) with them. As Hacking once said “If you can spray them, they are real!” I would say that if you can vaporize cities with them they are real.
Back to the point: It is, of course, not an argument against divine conservation that I express incredulity towards the idea. It seems an obviously dubious notion to me, but, of course, assertions of obviousness always do carry that “to me” rider, and so are not polemically potent to those for whom it is not obvious. But such statements do serve to state where we stand at the start of a discussion. Those who begin a discussion with very different priors (as you and I do) will diverge greatly on what seems plain or obvious. All we can do is state things as we see them and invite our interlocutors to supply reasons for seeing things otherwise. So, that is what I am doing here. I conclude, then, by putting the question to you:
Why does an electron, or any other fundamental physical entity, need divine aid to continue in existence?