"Between heresy and schism there is this difference, that heresy perverts dogma, while schism, by rebellion against the bishop, separates from the Church. Nevertheless there is no schism which does not trump up a heresy to justify its departure from the Church."
~ St. Jerome, (In Ep. ad Tit., iii, 10), remarking on how practically and historically, heresy and schism nearly always go hand in hand.