Bp. of Cagliari. An anti-Arian theologian, at the first session of the Council of Milan (354) he vehemently opposed the proposal to condemn Athanasius; his personal altercation with the Emp. Constantius that followed led to his banishment. After the accession of Julian, he was released (362) and made his way to Antioch, where by consecrating Paulinus bishop, he created a schism.