Science Fair Project Encyclopedia Pope Leo I By 431, as a
deacon, he occupied a sufficiently important position for Cyril
of Alexandria to apply to him in order that Rome's influence
should be thrown against the claims of Juvenal of Jerusalem to
patriarchal jurisdiction over Palestine -- unless this letter is
addressed rather to Pope Celestine I. About the same time
Johannes Cassianus dedicated to him the treatise against
Nestorius written at his request. But nothing shows more plainly
the confidence felt in him than his being chosen by the emperor
to settle the dispute between Aetius and Albinus, the two
highest officials in Gaul. During his absence on this mission,
Pope Sixtus III died (August 11, 440), and Leo was unanimously
elected by the people to succeed him. On September 29 he entered
upon a pontificate which was to be epoch-making for the
centralization of the government of the Church. Zeal for
orthodoxy An uncompromising foe of heresy, Leo found that in the
diocese of Aquileia, Pelagians were receiv