It was Augustine who first taught the damnation of infants (see Baptism, II.,1, § 3); but their sufferings, though eternal, are of the mildest character (De peccatorum meritis, i. 16); indeed, it seemed to him doubtful whether they were punished at all. The Roman Church, accepting Augustine’s conceptions of the necessity of baptism to salvation and of the mildness of the punishment of those infants who died unbaptized, agreed with him that they were sent to hell and assigned to them a distinct place in it, the limbus infantium or puerorum (see LIMBUS; cf. Thomas Aquinas, Summa, III.,quest. Ixviii. 2, Sup. quest. Ixxi. 7).
–The New Schaff-Herzog Encyclopedia of Religious Knowledge, Volume V. 1953: 490.