@ChristopherNoyesRoberts But politics require a definition of reality, and that definition differs among the players, because there’s no supreme authority to decree it.

I take it you’re not against authority, as long as it’s beneficent. Good luck! Libertarianism suffers from its basic tenet - that no one should be told what to do, backed up by that force monopoly you referred to. So libertarians have to compromise, knowing society cannot function with the chaos of every man for himself.