At the end of my article, I started moving toward a “solution” for which this question and @Eddie’s are not the kind of questions that have to be answered. @Tim_Reddish helpfully pointed out that the wave-particle duality problem is not a perfect metaphor, but insofar as it works, that would be like asking for an answer to how much wavelike-ness can your particle experiments accommodate.
My suggestion was that our talk about God’s providence (and I’d include God’s action here) are just that: our talk. And our talk about our freedom (and the lawlikeness of nature) are also our talk. These are discourses that have developed over many many generations of reflection on God, ourselves, and the world. But they are discourses that make use of different concepts. And if you’ll grant me the claim that our concepts are not one-to-one matches with reality, then it is entirely reasonable to think that different discourses may “carve up” the world in different ways. And though there will be significant overlap between these, there will be areas where they simply do not mesh together–they are incommensurable.
I think it is better to understand Aquinas’s primary and secondary causation in this way. It would take until Kant to get the epistemological framework for this sort of thing. But since Kant, we find a rich tradition of understanding that our language gets us into difficulties when we assume that it is reality, rather than a representation of reality. Folks I’ve been reading lately who are particularly germane to this problem include Cassirer, Buber, later Wittgenstein, John McDowell, Nancy Cartwright, Putnam, and Scruton.
I’m under no delusion that it will be satisfactory to you all to suggest that the problem of God’s relationship to the world is dissolved by this approach. But I think it points in the right direction to think more carefully about our talk about God and our talk about ourselves and the world. We adopt a very different perspective about humans when we operate on them as opposed to when we talk to them. We look for efficient and material causes to explain their behavior in the former, and we look for reasons to explain their behavior in the latter. We slide back and forth between these discourses quite easily without ultimately reconciling them. I’m suggesting we do something similar when we look at God’s providential guidance of history (including natural history), versus when we do science and interrogate the natural world to find its causes. Theology and science are our attempts to provide explanations that appeal to different concepts. I might even go so far as to say they have different ontologies in the transcendental idealist perspective I’m pushing.
Perhaps there is a higher level of discourse in which these lower level discourses can be incorporated the way quantum field theory resolves the wave-particle duality in light. But few of us incorporate the discourse of quantum field theory into our language and we are left with talking about light as a wave or as a particle. Remembering these are models frees us from having to provide an all-inclusive answer.