> That's all fine, but from the moment Maxwell's eq's are invoked, we enter an empirical framing, not a first principles one. Yes, of course. First principles

> That's all fine, but from the moment Maxwell's eq's are invoked, we enter an empirical framing, not a first principles one. Yes, of course. First principles only leads you to the conclusion that there is a reference speed. It tells you nothing about its actual value. In fact, first principles cannot rule out the possibility that the reference speed is infinite. They can only lead you to suspect that it might not be.