 which does not follow from either deductive logic or the probability axioms alone. But SR has been widely endorsed as unobjectionable, and according to some even undeniable, as a requirement of rationality (van Fraassen 1984: 248; Vickers 2000: 160; Koons 1992: 23—Skyrms 1980 sees as useful a version of it he calls Miller’s Principle, though he also shows it is subject to counterexamples).