The last step involves a transition from relative frequencies in finite sets to comparisons in infinite sets, and Oresme’s intuition, though sound, would need explication in the mathematical machinery of 1900, not that of 1350. The important thing is that the probability argument is perfectly clear, and perfectly correct; it is an instance of the probable argument schema: “The vast majority of As are Bs. This is an A (about which there is no more relevant information). Therefore, this is a B.”
