Liber contra Collatorem
Prosper of Aquitaine (390–463)
First published 1846
Liber contra Collatorem is a theological treatise by St. Prosper of Aquitaine written in defense of St. Augustine’s doctrine of grace against the views associated with John Cassian’s thirteenth Conference. Prosper examines a series of propositions concerning grace, free will, the origin of good intentions, merit, perseverance, and human cooperation with divine assistance, arguing that Cassian’s position departs from Catholic teaching whenever it attributes the beginnings of saving willing or action to unaided human nature. Throughout the work, he appeals extensively to Scripture, ecclesiastical authority, conciliar decisions, and earlier anti-Pelagian controversies, presenting Augustine’s theology as continuous with the doctrinal judgments of the Church. The treatise culminates in a systematic recapitulation of Cassian’s principal definitions and a broader defense of the primacy of divine grace in every stage of the Christian life, while affirming that grace does not abolish human freedom but restores, directs, and strengthens it.