Question
Why have you changed all the verbs referring to speech acts by Suárez to the past tense (“Suárez referred”, “Suárez concluded”, etc.)? Are you insisting on this as a “house style” across the volume? Otherwise I don’t like it. I prefer the present tense, and as far as I know there is no rule that requires the past tense.
Comment p1
“Formal”: I return to this term at the top of p2. I’ve added a sentence that I hope will explicate well enough the distinction I’m making between a theory that concerns formal characters and a theory that also tries to determine the nature of a thing (in this case the causal relation).   
Comment p2
I don’t know where you’re finding this supposed thesis. I’m not taking a position on the  question of the nature of causation. I’m observing that many recent accounts of causation proceed as if only formal characters had to be considered; these tend to identify themselves as following Hume, but there is nothing peculiarly Humean in denying that the causal relation is “nothing but” whatever relation satisfies the formal characters. As I say, I am putting forward no position myself. 
It seems to me you’ve given a pretty good counterexample to the claim that a thing that has no nature can have no formal charateristics—namely, fictional characters. “One can refuse to agree”, of course, but on what grounds? I would have thought that a fictional character had nothing but form, just as, on some accounts, numbers are all form and no content.
The paper doesn’t require me to exhibit a “need to agree” that a thing may have formal characters even if it lacks a nature. It requires only that the reader admit the possibility in the case of the causal relation. I would have that that was obvious given the recent tradition: vide, for example, Mackie or Suppes.
Comment p11
The source for the figure is me. I didn’t include it in the rtf. It’s a separate file called “deschene-suarez-figure1.png”. The intended dimensions are 4.38 in by 3.55 in (11.13 cm by 9.02 cm); the resolution is 600dpi. It can be made smaller so long as the text in the figure is legible.