Date: 355-360 C.E.

Hilary of Poitiers, who was instrumental in shaping the development of pro-Nicene theology in the West in the 4th century C.E., combined two separate works, a treatise on faith (De Fide) and a treatise against the Arians (Adversus Arianos), to create De Trinitate (On the Trinity); his chief theological contribution to the 4th-century Trinitarian debates.