I'd like to thank Prof. Feser for his continued patience in responding to my critique of Ross's argument. I've been very busy, but I finally had some time to look at his most recent response. He misconstrued the A, B, C, of my previous post (understandably, since I hadn't spelled them out clearly), and I began a long post carefully laying out the logic of my argument and why Feser's response didn't answer it. Then I realized that it did answer it, in spite of the misunderstanding about A, B, and C. The "purely physical" assumption is indeed the critical assumption in Ross's argument that I wasn't taking into account, and it does eliminate the Hilda objection in a non-question-begging way. I apologize to Prof. Feser for the unwarranted and unnecessary snark in my last post. I am hereby giving Hilda the boot.
I hope to return to my original epistemological objection (as time permits), but I wanted to get this apology out in a timely manner.
Crow is a dish best eaten warm.