The legacy of Augustine of Hippo (354-430) continues to shape Western Christian language about both the Trinity and the Church, yet scholars rarely treat these two topics as related in his work. In Augustine, the Trinity, and the Church, Adam Ployd argues that Augustine's ecclesiology drew upon his Trinitarian theology to a surprising degree; this connection appears most clearly in a series of sermons Augustine preached in 406-407 against the Donatists, the rival Christian communion in North Africa.

As he preached, Augustine deployed scriptural interpretations derived from his...