Bede synthesised and transmitted the learning from his predecessors, as well as made careful, judicious innovation in knowledge (such as recalculating the age of the earth—for which he was censured before surviving the heresy accusations and eventually having his views championed by Archbishop Ussher in the sixteenth century—see below) that had theological implications. In order to do this, he learned Greek and attempted to learn Hebrew. He spent time reading and rereading both the Old and the New Testaments. He mentions that he studied from a text of Jerome's Vulgate, which itself was from the Hebrew text. He also studied both the Latin and the Greek Fathers of the Church. In the monastic library at Jarrow were numerous books by theologians, including works by Basil, Cassian, John Chrysostom, Isidore of Seville, Origen, Gregory of Nazianzus, Augustine of Hippo, Jerome, Pope Gregory I, Ambrose of Milan, Cassiodorus, and Cyprian. He used these, in conjunction with the Biblical texts themselves, to write his commentaries and other theological works. He had a Latin translation by Evagrius of Athanasius's "Life of Antony" and a copy of Sulpicius Severus' "Life of St. Martin". He also used lesser known writers, such as Fulgentius, Julian of Eclanum, Tyconius, and Prosper of Aquitaine. Bede was the first to refer to Jerome, Augustine, Pope Gregory and Ambrose as the four Latin Fathers of the Church. It is clear from Bede's own comments that he felt his calling was to explain to his students and readers the theology and thoughts of the Church Fathers.