Severus was born in Pisidia, trained as a lawyer at Beirut, and was baptised only as an adult before turning to the monastic life in Palestine. He became patriarch of Antioch in 512, at the height of the argument over the Council of Chalcedon.
He rejected Chalcedon's formula, holding with Cyril of Alexandria that Christ is 'one incarnate nature of God the Word' — a position the Oriental Orthodox churches have held ever since, and which recent dialogue has increasingly recognised as a difference of language more than of substance. Deposed in 518, he fled to Egypt and spent the rest of his life there, writing letters and homilies that survive largely in Syriac translation. He remains the central theological authority of the Syriac and Coptic Orthodox traditions.