Prophets and Apostles could not resolve faith into Church authority; one species, one formal ground
Next, the Prophets and Apostles who first handed down sacred teaching and Scripture could not resolve the faith they had in God's Word into the Church's authority. They handed that teaching to the Church; they did not receive it as something the Church had already recommended. And it can happen, at least outside the ordinary course, that someone believes the Gospel though taught by no man — happening, say, on a Gospel codex. In that case his faith could not take as foundation a Church authority whose testimony he had never heard.
Yet there is one faith of all. Our faith does not differ in species from the faith of the Prophets and Apostles, or of those taught by God immediately. But our faith would not be the same as theirs if it had another foundation and another formal ground of believing. One species of faith has one proper and principal foundation. As the Schools put it, it does not have diverse formal grounds of believing.
Latin
XXII. Deinde Prophetae atque Apostoli, qui primi doctrinam sacram et Scripturam tradiderunt, fidem illam, quam verbo Dei habebant, non poterant in Ecclesiae authoritatem resolvere: quandoquidem doctrinam illam Ecclesiae tradebant, non vero ab Ecclesia commendatam accipiebant. Et fieri potest, saltem extra ordinem, ut quis Evangelio credat a nullo homine doctus, sed forte in aliquem Evangelii codicem incidens. Quo casu fides istius hominis pro fundamento non posset habere authoritatem Ecclesiae, cujus testimonium nunquam audivisset. Et tamen una est omnium fides. Neque specie differt fides nostra a fide Prophetarum et Apostolorum, et eorum qui a Deo immediate docerentur. Fides autem nostra non esset eadem cum eorum fide, si fundamentum aliud haberet, et aliam formalem credendi rationem. Unius enim speciei fidei unicum est proprium et praecipuum fundamentum: nec sunt ejus, ut loquuntur Scholae, diversae formales credendi rationes.