His work is the only life of Ambrose based on a contemporary account, and was written at the request of Augustine of Hippo;[1] it is dated to 422 AD.
[2] In Carthage in 411 he had opposed Caelestius, a Pelagian.
[3] The formal proceedings were described by Augustine in On Original Sin.
Paulinus set up six theses defining Pelagian views as heresy; Caelestius gave up on becoming a presbyter in Carthage, instead he moved to Ephesus[4] Paulinus was summoned to Rome in 417, to justify himself.
[5] With local backing, he declined to appear before Pope Zosimus; in 418 the Pope took into account the measure of support for the anti-Pelagian position, and condemned both Caelestus and Pelagius.