An extended passage, but it's worth quoting:
But some one will say, perhaps, Shall there, then, be no progress in Christ’s Church? Certainly; all possible progress. For what being is there, so envious of men, so full of hatred to God, who would seek to forbid it? Yet on condition that it be real progress, not alteration of the faith. For progress requires that the subject be enlarged n itself, alteration, that it be transformed into something else. The intelligence, then, the knowledge, the wisdom, as well of individuals as of all, as well of one man as of the whole Church, ought, in the course of ages and centuries, to increase and make much and vigorous progress; but yet only in its own kind; that is to say, in the same doctrine, in the same sense, and in the same meaning.
The growth of religion in the soul must be analogous to the growth of the body, which, though in process of years it is developed and attains its full size, yet remains still the same....This, then, is undoubtedly the true and legitimate rule of progress, this the established and most beautiful order of growth, that mature age ever develops in the man those parts and forms which the wisdom of the Creator had already framed beforehand in the infant. Whereas, if the human form were changed into some shape belonging to another kind, or at any rate, if the number of its limbs were increased or diminished, the result would be that the whole body would become either a wreck or a monster, or, at the least, would be impaired and enfeebled.
In like manner, it behoves Christian doctrine to follow the same laws of progress, so as to be consolidated by years, enlarged by time, refined by age, and yet, withal, to continue uncorrupt and unadulterate, complete and perfect in all the measurement of its parts, and, so to speak, in all its proper members and senses, admitting no change, no waste of its distinctive property, no variation in its limits....
Therefore, whatever has been sown by the fidelity of the Fathers in this husbandry of God’s Church, the same ought to be cultivated and taken care of by the industry of their children, the same ought to flourish and ripen, the same ought to advance and go forward to perfection. For it is right that those ancient doctrines of heavenly philosophy should, as time goes on, be cared for, smoothed, polished; but not that they should be changed, not that they should be maimed, not that they should be mutilated. They may receive proof, illustration, definiteness; but they must retain withal their completeness, their integrity, their characteristic properties.
Commonitorium Chapter XXIII. I will be discussing this at some point.