In this letter Jerome congratulates Alypius and Augustine on their success in strangling the heresy of Cælestius, the co-adjutor of Pelagius, and states that, if he can find time and secretaries, he hopes to write a refutation of the absurd errors of the Pelagian pseudodeacon Annianus. The date is 419 a.d. This letter is among those of Augustine, number 202.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 2, vol. 6 (Schaff and Wace, 1893), public domain (Public domain).