Updated: Dec 16, 2021
4. The Authority of the Epistle asserted against the ancient and more recent gainsayers.
Therefore, there is no occasion either of denying the Divinity of this Epistle, because formerly heretics, Marcion, Arius, and others, and indeed even the Latins rashly, as Eusebius testifies, pled that it favored the Novatians: or of loading it with malignant suspicions, as do the Socinians, Enjedinus, Schlichting, and others at this day, because the author is uncertain. For the signs of the authorship of Paul are not obscure. But whether the author be Paul, or some other, it derogates nothing from its authority, which depends on the Holy Spirit, the primary author. Indeed, not one argument of Canonical Divinity is here missing. The doctrine that is here delivered is as exalted as can be. What in other parts of Scripture are touched in passing, are here treated and demonstrated with greater fullness. The veil is removed from Moses, and the most profound explanations of his mysteries are laid out. The Scope/Goal is altogether Divine, namely, the promotion of the glory of God in Christ, the end of the law for righteousness to all believers. The style is grave, simple, full of Majesty, and accommodated to the sublime matters that it treats. Also, Theodoret testifies that the Epistle was received from the beginning in the Church as Canonical, without the connected reason, on account of which οἱ ἀντιλέγοντες, the gainsayers, have attempted to kill it. Tertullian praises it as Divine; and, having been sent into Grecia, it was read by the Greeks, although the Latins, hindered by prejudice, allowed its authority to be approved more slowly.
 Arius (c. 250-336) was a presbyter of the church in Alexandria, Egypt. He denied the Son to be of one substance, and co-equal Deity, with the Father. His views precipitated the Arian controversy, and led to the calling of the First Ecumenical Council at Nicea (325).  Novatian (c. 200-258) was a priest and scholar. He argued against readmission to the church for those who had lapsed during persecution, and this brought him into conflict with the Roman Bishop Cornelius. Novatian was excommunicated. The Novatians broke away from the Catholic Church, even rebaptizing converts.  Fausto Paolo Sozzini, or Faustus Socinus (1539-1604), was the father of Socinianism, a rationalistic heresy (denying the Deity of Christ, the satisfaction theory of the atonement, etc.), an aberration of the Reformation.  Georgius Enjedinus (died 1597) was an overseer of the Socinians churches of Transylvania.  Jonas Schlichting (1592-1661) was a theologian of the Socinian Polish Brethren. He wrote commentaries on most of the books of the New Testament.  See 2 Corinthians 3:13-16.  See Romans 10:4.
Dr. Dilday's Lecture: "A Pauline Miscellany, Part 5"