St. Tertullian

Tertullian was born around 155 at Carthage in Roman North Africa (in modern Tunisia), and died sometime after 220. A convert of great rhetorical power and sharp wit, he became the first major Christian author to write in Latin rather than Greek, and is often called the 'father of Latin theology.' His Apology brilliantly defended Christians against the slanders of the pagan world, and he coined much of the Latin vocabulary later used to express the faith — including the very word 'Trinity' (Trinitas) and the language of 'person' and 'substance.'

His writings profoundly shaped Western Christian thought, yet his rigorist temperament led him in later life to embrace Montanism, a sect the Church judged heretical for its excesses. For this reason, despite his enormous influence, he was never canonized and is not venerated as a saint; the Church esteems his genius and his early witness while noting the errors into which his severity finally drew him.