Ames: faith-in-itself requires greater certainty than fiducia born from faith
Ames further distinguishes faith-in-itself from fiducia that rises from faith — the trust by which we grasp a present good or hope a future one.
Greater certainty belongs to faith itself than to that born fiducia, even when the fiducia is loosely called faith.
So when believers are said to be divinely certain of accepted grace or coming salvation, Ames means fiducia from faith, not justifying faith as such — and that fiducia has lesser certainty.
Latin
CXXXVII. Praeterea indicat Amesius distinguendum esse, inter fidem in sese, & respectu actuum qui ad ejus essentiam requiruntur, consideratam; & inter fiduciam ex fide orientem, per quam vel praesens aliquod bonum apprehendimus, vel futurum speramus. Majorem autem certitudinis gradum in ipsa fide esse & requiri, quam in fiducia ex fide nascente, per quam, vel de bono praesenti, vel de futuro persuasi sumus; licet eadem fiducia, fidei quoque nomine designetur. Jam vero juxta Amesium, quum fideles dicuntur fide divina certi, vel de accepta gratia, vel de salute obtinenda, per fidem ibi intelligenda est, non fides justificans & salvifica in sese, sed fiducia ex fide oriens, per quam, vel apprehendimus jam concessam a Deo remissionem peccatorum, vel futuram salutem speramus. Proinde fiduciae isti, quae ex fide nascitur, ex mente Amesii minor competit certitudo, quam fidei, si in sese consideretur.