Little is known of the life of Cyril before he became bishop. It is believed he was born about the year 313 or 315 AD. He was raised in Jerusalem and given a good education, especially in the Scriptures. About the year 335, he was ordained deacon by St Macarius of Jerusalem, and ordained priest about eight years later by Bishop St Maximus. He was given the task of catechising during Lent those preparing for Baptism, and during the Easter season, the newly baptised. His catechetical texts remain valuable as examples of the ritual and theology of the Church in the mid-fourth century.

About the year 350 he succeeded St Maximus as Bishop of Jerusalem. Through the nature of his conciliatory disposition, while opposed to Arianism, he was not quite ready to accept the uncompromising term homoousios (from the Greek meaning ‘consubstantial’ and indicating that Jesus shared the same divine nature with the Father).

But he distanced himself from his archbishop, Acacius of Caesaraea, who favoured the position of Arius, and Cyril favoured the so-called Eusebians who were anti-Arian. This displeased Acacius, and a council held under Acacius accused Cyril of insubordination and selling church property to help the poor. He was forced to retire to Tarsus. Then in the following year, the Council of Seleucia, at which Cyril was present, deposed Acacius.

In 360 AD, Acacius was again in control and Cyril was sent away for another year, until the accession of the emperor Julian allowed him to come back. Then in the year 367, the Arian emperor Valens banished him again. But Cyril was able to return with the accession of the emperor Gratian, and returned to find Jerusalem torn with heresy, schism and strife, and wracked with crime. Even St Gregory of Nyssa, who was sent to help, left in despair.

Cyril and Gregory both went to the (second ecumenical) Council of Constantinople, where the amended form of the Nicene Creed was promulgated. Cyril now accepted the word ‘consubstantial’. Some said it was an act of repentance, but the bishops of the Council praised him as a champion of orthodoxy against the Arians. Though not friendly with St Athanasius of Alexandria, the greatest defender of orthodoxy against the Arians, Cyril may be counted among those whom Athanasius called “brothers, who mean what we mean, and differ only about the word” (i.e. ‘consubstantial’).

He remained in his post until his death in 386. In 1883, St. Cyril was declared a Doctor of the Church by Pope Leo XIII.