The school of thought in which a movie may approach the level of Braveheart, but may never reach it, only head towards the theoretical infinity where Braveheart resides.
It should be noted that the x-axis on which the Braveheart Asymptote exists does not necessarily refer to a single idea (i.e. quality, awesomeness, number of bagpipes) but rather everything that Braveheart is and all other movies aspire to be.
Dude 1: Independance Day was a fantastic movie, maybe better than Braveheart.
Dude 2: Unfortuntaly, that is impossible
Dude 1: Why's that?
Dude 2: Because of the Braveheart Asymptote.
Dude 1: Oh, yeah, ok I get it.