[4] The first recorded act of Liberius was, after a synod had been held at Rome, to write to Emperor Constantius II, then in quarters at Arles (353–354), asking that a council might be called at Aquileia with reference to the affairs of Athanasius of Alexandria, but his messenger Vincentius of Capua was compelled by the emperor at a conciliabulum held in Arles to subscribe against his will to a condemnation of the orthodox patriarch of Alexandria.
In 366, Liberius gave a favourable reception to a deputation of the Eastern episcopate, and admitted into his communion the more moderate of the old Arian party.
[3] Some historians have postulated that Liberius resigned the papacy in 365, in order to make sense of the pontificate of Felix II, who has since been regarded as an antipope.
[10] Pope Pius IX noted in his 1863 encyclical Quartus supra that Liberius was falsely accused by the Arians and he had refused to condemn Athanasius of Alexandria.
[14] In Coptic Christianity, the Departure of St Liberius the Bishop of Rome is commemorated on 4 Pi Kogi Enavot.