City Readers Digital Historic Collections at the New York Society Library

Tertullian (/tərˈtʌliən/), full name Quintus Septimius Florens Tertullianus, c. 155 – c. 240 AD, was a prolific early Christian author from Carthage in the Roman province of Africa. He is the first Christian author to produce an extensive corpus of Latin Christian literature. He also was a notable early Christian apologist and a polemicist against heresy, including contemporary Christian Gnosticism. Tertullian has been called "the father of Latin Christianity" and "the founder of Western theology."

Though conservative, he did originate and advance new theology to the early Church. He is perhaps most famous for being the oldest extant Latin writer to use the term Trinity (Latin: Trinitas), though a similar word had been used earlier in Greek, and giving the oldest extant formulation of the Trinitarian terminology later adopted as the modified Nicene Creed at the 2nd Ecumenical Council, the First Council of Constantinople in 381 AD/CE, or as the Athanasian Creed, or both. Other Latin formulations that first appear in his work are "three persons, one substance" as the Latin "tres personae, una substantia" (itself from the Koine Greek "treis hypostases, homoousios"). He wrote his trinitarian formula after becoming a Montanist. However, unlike many Church fathers, he was never recognized as a saint by the Church, as several of his teachings on issues such as remarriage for widows and fleeing from persecution (both of which he condemned) contradicted the teachings of the Church.