Cyril of Alexandria
376 — 444
Cyril of Alexandria was the formidable Patriarch of Alexandria from 412 to 444 and the decisive voice at the Council of Ephesus in 431, which defined Mary as Theotokos — 'God-Bearer' — and condemned the heresy of Nestorius. A relentless defender of Christ's full divinity and a controversial figure even in his own time, he is counted among the Doctors of the Church with the titles 'Pillar of Faith' and 'Seal of all the Fathers.'