Heidegger's Bible Handbook: Romans: The Style of Paul's Epistles
4. The style, and manner and character, of the speech of the same Epistles. In what sense Saint Peter called some things in them δυσνόητα, hard to be understood?
The style of the Pauline Epistles is not grand, sublime, or inflated, since this is not suited to the doctrine of the Gospel, and faith, having its gravitas, not so much in the wisdom of men, but in the power of God: nor base, rough, and rude, which the Wise Men of this world could rightfully despise; since it is apparent that, on account of eloquence, Paul was esteemed by the men of Lystra even as Mercury, Acts 14:12: but, between the extremes, temperate, moderate, grave in doctrine, pregnant and dense with thoughts, rotund in arguments, pleasant in affections, and elegant and effective in words, familiar, plane, equal, completely suited to the art of Heavenly Rhetoric, and to an Apostle of Christ of the first rank, inferior to no one in renown of doctrine and eloquence. And with good reason does Saint Ambrose exclaim, Sermons 68: What Epistle of Paul is not sweeter than honey? whiter than milk? Eusebius, Historia Ecclesiastica, book 24, calls it: Πάντων ἐν παρασκευῆ δυνατώτατον λόγων, νοήμασι δὲ ἱκανώτατον, in structure the most powerful of all speeches, in sense the most instructive. But Jerome also, ad Pammachium, does not dread to mark it as the trumpet of the Gospel, the roaring of our lion, the thunder of the nations, the stream of Christian eloquence. The Most Learned Glassius, in his Philologia Sacra, page 344, observes certain peculiarities concerning the style of the Epistles of Paul, of which sort are, the Paul attracts hearers to himself with wonderful and more than maternal allurements: that in rebukes he with consummate wisdom tempers gravity with lenience: that he repeatedly makes use of forms of speech peculiar, and not in common use by others: that he makes use of certain words with a new signification and sense. In 2 Peter 3:16, Saint Peter said that in them occur δυσνόητά τινα, some things hard to be understood; yet they are so hard and difficult, not on account of obscurity of speech, but on account of the sublimity of the matters, and the defect of the human mind, a defect to be explained by the infirmity of the one not immediately perceiving, or by the malice of one perverting. To which pertain some oracles concerning the scoffers of the last time, the final judgment, the coming of Christ, the end of the world, the renewal of the Universe, which sort of things Saint Peter handles in that place.
 See 1 Corinthians 2:5.