This is Liberius, Bishop of Rome a.d. 352–366, who temporized with Arianism. [St. Hil. Pict. Fragm. VI.; St. Athan. Apol. C. Arian. 89; Hist. Arian. 41; St. Jerome, De Vir. Ill. 97, etc.] He subsequently returned to the Catholic teaching and atoned by later acts for his temporary weakness.