Bishop of Antioch (in modern Turkey), and an early Christian apologist. Originally a philosopher in the eastern Roman Empire, he began to study the Scriptures with the intention of attacking the Christian faith but was soon converted. A gifted apologist, he was the author of an Apology in three books and addressed to Autolycus (the only work of his writings to survive). It seeks to demonstrate the superiority of Christianity over the immoral myths of pagan religion. It is also noted for its development of the doctrine of the Logos (Word) as first enunciated in the Gospel of John and to express the word Triad when describing the relationship of the Father, the Son, and the Holy Spirit.

Feastday: October 13