Faustinus’ life is not well known. The little information about him – and Marcellinus whom he is related to – come from Faustinus’ work itself, especially the Libellus Precum. Only Gennadius of Marseille (Vir. ill. 16) and Isidore of Seville (Vir. ill. 5.6–7; 14.16), who knew his works, spoke of them. Both priests, Faustinus and Marcellinus, were considered “Luciferians” (Faust. Libel. 84; 86; Luciferians) by the bishop of the Church of Rome, Damasus I (366–d. Dec 11, 38…