Infallible Church-judge is a circle — prove it without Scripture and tradition
If only a present, infallible Church authority can certify true Scripture and tradition against the false and apocryphal, that authority must be known first — before Scripture and tradition, and without leaning on their witness.
So ask Rome to prove papal or conciliar authority from somewhere other than Scripture and tradition.
They say they defer to Scripture and traditions as divine because Pope or Council so moves them — which leaves the question: what finally makes them believe the Church is infallible when it judges Scripture and tradition?
Latin
XLII. Adde quod, si certi reddimur de veris Scripturis, & traditionibus per authoritatem quandam infallibilem quae est in Ecclesia praesenti, sine qua non possunt a nobis falsae & apocryphae discerni certo & infallibiliter, necesse est ut prius nobis constet de authoritate illa infallibili, quam de ipsa Scriptura atque traditione, & seposita Scripturae atque traditionis authoritate & testimonio nobis innotescere possit. Ideoque jure possumus Pontificios rogare, ut authoritatem illam, quam Pontifici sive Concilio tribuunt, aliunde nobis probent, quam ex ipsa Scriptura atque traditione, quandoquidem profitentur se Pontificis sive Concilii authoritate moveri, ut tantum traditionibus & Scripturae deferant, & tam Scripturas quam traditiones tanquam divinas amplectantur. Quid ergo tandem erit illud propter quod Ecclesiam suam infallibilem esse credunt dum de traditionibus & Scripturis judicat?