Tertullian

Quintus Septimius Florens Tertullianus was born at Carthage around 155, trained in Roman law and rhetoric, and converted as an adult. Jerome says his father was an officer of the proconsul and that Tertullian himself became a presbyter; modern scholars doubt both details, and Tertullian never mentions either. What is beyond doubt is the training. Everything he wrote reads like a brief.

He was the first major Christian author to write in Latin, and because he was first he had to build the vocabulary. He is the earliest writer known to use trinitas, Trinity, of God, and he supplied the formula the church has used ever since: one substance in three persons, substantia and persona, both terms taken straight out of Roman law where they meant an estate and a party to a case. Sacramentum, satisfaction, merit, a great deal of the working language of Western theology comes out of this one man's desk.

His Apology, written about 197 and addressed to the governors of the empire, is the most aggressive defense of Christians ever written. He argues the trials are illegal on Rome's own terms, that Christians are convicted for a name and not an act, that the same magistrates enforce laws they privately despise. Then he turns it: kill us, torture us, condemn us, grind us to powder, your cruelty proves nothing except our innocence, and the more you mow us down the more we grow. The blood of Christians is seed.

He wrote against Marcion, who had cut the Old Testament and most of the New out of the Bible, in five books. He wrote against Praxeas, who taught that the Father suffered on the cross. He wrote On the Prescription of Heretics, arguing that heretics had no right even to appeal to Scripture since the Scripture belonged to the churches the apostles founded, and asked the question that has been quoted ever since: what has Athens to do with Jerusalem, the Academy with the Church.

He wrote on baptism, on prayer, on patience, on the dress of women, on the soldier's crown, on whether a Christian may run from persecution. His answer to that last one was no.

Around 207 he joined the New Prophecy, the movement called Montanism, which held that the Spirit was still speaking and demanded a stricter discipline than the bishops would enforce. He never came back. The church that took his vocabulary never canonized him.

He died about 220, an old man, still writing.

Sources: Tertullian, Apology, Against Marcion, Against Praxeas, On the Prescription of Heretics (Ante-Nicene Fathers, vols. 3–4); Jerome, On Illustrious Men 53; Philip Schaff, History of the Christian Church, vol. 2.