Sean Carroll in Preposterous Universe:
It’s too easy to take laws of nature for granted. Sure, gravity is pulling us toward Earth today; but how do we know it won’t be pushing us away tomorrow? We extrapolate from past experience to future expectation, but what allows us to do that? “Humeans” (after David Hume, not a misspelling of “human”) think that what exists is just what actually happens in the universe, and the laws are simply convenient summaries of what happens. “Anti-Humeans” think that the laws have a reality of their own, bringing what happens next into existence. The debate has implications for the notion of possible worlds, and thus for counterfactuals and causation — would Y have happened if X hadn’t happened first? Ned Hall and I have a deep conversation that started out being about causation, but we quickly realized we had to get a bunch of interesting ideas on the table first. What we talk about helps clarify how we should think about our reality and others.