“‘Touched inwardly with sorrow of heart’ [Gen. 6:6], ‘we are filled with the bitterness of wormwood’ [cf. Lam. 3:15], because as it has been brought to our attention, certain ones among you, distended like a skin by the spirit of vanity, are working with profane novelty to pass beyond the boundaries which thy fathers have set [cf. Prov. 22:28], the understanding of the heavenly page limited by the fixed boundaries of expositions in the studies of the Holy Fathers by inclining toward the philosophical doctrine of natural things, which it is not only rash but even profane to transgress; (they are doing this) for a show of knowledge, not for any profit to their hearers; so that they seem to be not taught of God or speakers of God, but rather revealed as God. For, although they ought to explain theology according to the approved traditions of the saints and not with carnal weapons, ‘yet with (weapons) powerful for God to destroy every height exalting itself against the knowledge of God and to lead back into captivity every understanding unto the obedience of Christ’ [cf. 2 Cor. 10:4 f.], they themselves ‘led away by various and strange doctrines’ [cf.Heb. 13:9] reduce the ‘head to the tail’ [cf. Deut. 28:13, 44] and they force the queen to be servant to the handmaid, that is, by earthly documents attributing the heavenly, which is of grace, to nature.” (Denz. 442)
Pope Gregory IX, From the letter “Ab Aegyptiis” to the theologians of Paris, July 7, 1228