For instance, there's nothing in the physics that rules out a version of Earth is which, by sheerest coincidence, magic appeared to work. Or to put it another way, in which physical laws appeared, for some time, to be different than what they "actually" are. Of course, for every such universe, there would be an much larger set of ones where that "magic" suddenly ceased "working" one day.

It's even conceivable that we live in such a universe. Maybe, back in the Middle Ages, magic *did* "work". Or for a scarier twist, maybe *we* will wake up one morning and discover that what we held to be physical law turns out to have just been a series of coincidences.