One problem with adjudicating Mage: the Ascension is that it is very hard to distinguish between what the Storyteller believes is possible in real life and what the fictional NPCs believe is possible in the game.
For example, the Storyteller might be an atheist who disbelieves the reports that Saint Joseph of Cupertino flew through the air by the miraculous power of faith. If that is the case, it will be very hard for that Storyteller to allow players to even discuss those reports of miracles. The tendency is for such a Storyteller to hear “flying” and automatically say “fantasy.” The Storyteller won’t even discuss coincidental, vulgar without witnesses, or vulgar with witnesses. The Storyteller will very often say, “Flying is something Superman does, and this is not a four-color superhero game, pick a different effect.”
Even in the loosest version of Mage rules, there is language that would seem to discourage miracles. E.g. p.172 of 1st edition Mage: “The player must devise a means by which the same effect can result through a different appearance. The description can only involve “realistic” events, and must be at least remotely believable.”
However, there are many other relevant passages in many rulebooks. Page 182 of 2nd Edition Mage notes that mythic threads and particular foci may make the difference between vulgar and coincidental. Page 185 of the same book notes “Away from the cities, people still believe in things other than Science. … Christian ministers … can get away with more than they normally would be able to. … flying on broomsticks is never a good idea these days.” The rules leave it open to interpretation whether flying in the traditional Christian manner of Saint Joseph of Cupertino is just as vulgar as flying in the pagan manner of a broomstick-rider.
The practical difficulty in running Mage is that various participants will have drastically different notions of what is remotely believable. Some Storytellers will say that flying humans can be coincidental (if they resemble Saint Joseph of Cupertino) and other Storytellers will say that flying humans are always vulgar.