Roman by birth and a philosopher. During his pontificate he is said to have instituted the Minor Orders of the ecclesiastical hierarchy and to have distributed the various offices of the clergy. Some decrees are also attributed to him, but these are certainly spurious. From St Irenaeus it is known that during his pontificate the Gnostics Valentinus and Cerdon came to Rome to spread their errors. The latter even managed, by means of a cunning profession of faith, to be received into the community, but was later unmasked and expelled.
BIBL.: Eusebius, Hist. eccl., IV, 10 sq.; Acta SS. Iannarii, I, Paris 1863, p. 665 sq.; Lib. Pont., I, p. 131; E. Amann, s. V. in DThC. VII, col. 356 sq.; Martyrologium Romanum, p. 15.
AGOSTINO AMORE