Ambrosiaster, or Pseudo-Ambrosius, is the name ascribed to the unknown author of Commentaria in Epistolas Beati Pauli, an early commentary on the writings of the apostle Paul. The work had been attributed to St. Ambrose, Bishop of Milan, who died in 397; however, in 1527, the esteemed scholar, theologian, and philosopher Desiderius Erasmus questioned Ambrose’s authorship, and his considered verdict has since been widely accepted by scholars. As doubt surrounds the commentary’s authorship, the name Ambrosiaster, or Pseudo-Ambrosius, is used.
The real Ambrosius (as opposed to Ambrosiaster) was Aurelius Ambrosius, also known as Ambrose of Milan. He was bishop of Milan during the fourth century. Prior to becoming a prominent theologian, Ambrose held a position in the Roman government as a consular prefect. As a youth, he studied law, literature, and rhetoric. His reputation as a gifted orator motivated Augustine, who was then a non-believer, to hear him speak. As bishop of Milan, Ambrose was regarded for his generosity toward the poor, his stand against the Arian heresy, and his strict adherence to ethical conduct. But Ambrose is probably best known today for his role in Augustine’s conversion to Christianity.
The manuscript attributed to Ambrosiaster offers no hint as to its author. Internal evidence suggests the commentary was written during the pontificate of Damascus (AD 366—384). The biblical quotations predate the Latin Vulgate; additionally, the referencing of ecclesiastical writers such as Tertullian, Cyprian, and Victorinus also supports the mid- to late-fourth-century dating. Adding further confusion to the question of authorship, Augustine credited portions of the commentary on Paul’s letter to the Romans to Sanctus Hilarius.
Considered one of the outstanding Dominican scholars of his time, Sixtus Senensis, or Sixtus of Siena, described the Commentaria in Epistolas Beati Pauli as “brief in words, but weighty in matter.” As previously mentioned, the biblical references in Ambrosiaster’s work predate the Latin Vulgate; thus, the commentary has played an important role in textual criticism. Regardless of authorship, the Commentaria was hailed by scholars such as Augustine and Jerome for the quality of its exegesis.