The argument is a fallacy that overturns every first rule of faith, including Rome's
I answer that this is a mere fallacy with which Rome can be pressed as hard as we can. Turn it back on them: the Church's voice and testimony is not the supreme rule of faith; its authority for us hangs on some other principle of faith better known and more certain.
There must be another divine testimony, clearer and surer than the Church's, by which the Church's testimony itself is established — because the Church's authority cannot be proved by the Church's own word. The same thing cannot be both better known and less known than itself; nothing from the Church's testimony proves anything of that authority, or still doubting it.
If the argument is worth anything, it overturns faith altogether. No rule of faith can be offered as first and supreme without leaving room for the same objection.
Latin
III. Respondeo hoc argumentum meram esse fallaciam qua Pontificii possunt aeque ac nos urgeri. Sic enim in ipsos retorqueri potest. Ecclesiae vox et testimonium non est suprema fidei regula, sed ejus authoritas ab alio quodam fidei principio quoad nos notiori et certiori pendet. Nam necesse est ut sit testimonium aliud divinum, Ecclesiae testimonio notius et certius, per quod de Ecclesiae testimonio constet. Et hoc quia Ecclesiae authoritas et testimonium per ipsius Ecclesiae testimonium probari non potest. Cum idem seipso non sit notius et ignotius, neque authoritatem Ecclesiae ignoranti, aut de authoritate Ecclesiae dubitanti, quicquam possit ex testimonio Ecclesiae probari. Itaque, si quicquam valet hoc argumentum, omnem prorsus fidem subvertit: quandoquidem non potest ulla proferri fidei regula, tanquam prima et suprema, contra quam non liceat simili argumento uti.