We are here speaking in open disapproval of that false system of philosophy, not so long ago introduced, by which, because of an extended and unbridled desire of novelty, truth is not sought where it truly resides, and, with a disregard for the holy and apostolic traditions, other vain, futile, uncertain doctrines, not approved by the Church are accepted as true, on which very vain men mistakenly think that truth itself is supported and sustained.
Pope Gregory XVIBeyond a doubt, they perish eternally who do not keep the Catholic faith entire and unchanged.
Pope Gregory XVIThat rule must be absolutely observed which states that, except for the most serious reasons and with the Apostolic See, no innovations are to be introduced into the holy rites of the liturgy.
Pope Gregory XVI