Our St. Louis reading group on Lange's book (Laws and Lawmakers: Science, Metaphysics, and the Laws of Nature, OUP, 2009) is over. As I mentioned, Lange argues that the truthmakers for laws of nature are "subjunctive facts".
I still don't understand what a subjunctive fact is supposed to be; Lange doesn't shed much light on this. A subjunctive statement is a statement about what else would be the case, were something the case. Generally, the supposition of a subjunctive statement (i.e., what follows the "if" in "if something were the case") is contrary to fact. So a subjunctive fact is (usually) a fact linking two counterfactual facts, or a fact about contrary-to-fact facts. ???
Lange talks about regular categorical facts, and he seems to make sense of them, like many other people, as instantiations of categorical properties at a time. (I'm reading between the lines here, as Lange doesn't discuss this explicitly; but he does mention categorical properties occasionally.) Lange also occasionally mentions dispositions, but as far as I can see he doesn't draw any connection between dispositions and "subjunctive facts".
The best I can do is to suggest that subjunctive facts are dispositional facts -- facts dependent on the instantiation of a disposition (i.e., a power) at a time. Since dispositions have different manifestations under different conditions, the instantiation of a disposition can ground many different "subjunctive facts".
I would find Lange's view clearer and more persuasive if he said that the truthmakers for laws are dispositions/powers. Of course, other people have said this before, so his view would sound less radical if framed in terms of dispositions/powers. I believe that Lange would reject my gloss on subjunctive facts because he insists that "subjunctive facts" are ontologically primitive. But why should they be ontologically primitive, when (i) regular categorical facts do not seem to be ontologically primitive even by Lange's own lights and (ii) there is a straightforward account available in terms of dispositions/powers? And how are we supposed to make sense of them if not in terms of dispositions/powers? If I'm going to take something as primitive, I'd rather take powers than "subjunctive facts".
Any thoughts on this?
PS: While I'm here, I'll answer a question by anonymous posted to the earlier thread on this topic.
"Does Lange really say that laws are ontologically grounded in counterfactuals? This would be strange, since counterfactuals are linguistic entities (sentences or propositions) and laws are non-linguistic general facts."
No, Lange says laws are ontologically grounded not by counterfactuals tout court but by counterfactual facts, or "subjunctive facts."