Closer application: the doubt syllogism and two senses of uncertainty
But to deal more closely now, apply this to the argument on the table. It runs like this: what is doubtful and uncertain to us of itself cannot be firmly believed unless some higher authority confirms it; Scripture of itself is doubtful and uncertain to us; therefore some higher authority must confirm it — and that can only be the Church.
I answer that something can be called doubtful and uncertain to us in two respects: with respect to faith, and with respect to human reason.
Uncertain for faith is what God has not revealed and inspired. Uncertain for human reason is what cannot be shown by necessary and evident proofs. So distinguish the minor: Scripture of itself is doubtful and uncertain to us. Said of human reason, that can be granted; said of faith, it must be denied.
Scripture can of course be urged on human reason with many good, weighty arguments. Because those arguments are not logical or mathematical demonstrations, we allow that Scripture may be called uncertain to human reason. But it is false that what reason finds uncertain and indemonstrable cannot be certain for faith. What can be demonstrated is, to that extent, not a matter of faith at all.
Latin
XXIII. Sed, ut jam pressius agamus, ista sunt ad argumentum propositum applicanda. Argumentum fuit ejusmodi. Quod ex se nobis est dubium & incertum firma fide a nobis apprehendi non potest, nisi authoritate aliqua superiori confirmetur. Sed Scriptura ex se nobis dubia & incerta est. Ergo necesse est eam authoritate aliqua superiori confirmari. Quae alia esse non potest quam Ecclesiae authoritas. Respondeo aliquid nobis dubium & incertum dici potest duplici respectu. Nempe fidei respectu: deinde respectu rationis humanae. Fidei incertum est quod a Deo revelatum & inspiratum non est. At rationi humanae incertum est quod demonstrari non potest argumentis necessariis & evidentibus. Itaque distinguenda minor, Scriptura ex se nobis dubia & incerta. Nam, si illud nobis dicatur, respectu rationis humanae concedi potest, si vero respectu fidei neganda est. Quamvis enim Scriptura rationi etiam humanae suaderi & commendari possit multis bonis & validis argumentis: Attamen quia ista argumenta logice & mathematice demonstrativa non sunt, eatenus patimur Scripturam dici humanae rationi incertam. Sed falsum est fidei non posse esse certum quod rationi incertum est, nec demonstrari potest. Imo quod demonstrari potest eatenus res fidei non est.