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During the first four centuries of the Christian era, the existence of purgatory was commonly taught in the Church, as seen in its universal practice of offering prayers and sacrifices for the dead.
The most ancient liturgies illustrate the custom in such prayers as the following: "Let us pray for our brothers who have fallen asleep in Christ, that the God of the highest charity towards men, who has summoned the soul of the deceased, may forgive him all his sin and, rendered well-disposed and friendly towards him, may call him to the assembly of the living" (Apostolic Constitutions, 8:41).
Equally ancient are the inscriptions found in the catacombs, which provide numerous examples of how the faithful offered prayers for their departed relatives and friends. Thus we read from engravings going back to the second century such invocations as: "Would that God might refresh your spirit . . . Ursula, may you be received by Christ . . . Victoria, may your spirit be at rest in good . . . Kalemir, may God grant peace to your spirit and that of your sister, Hildare . . . Timothy, may the eternal life be yours in Christ."
Writers before Augustine explicitly teach that souls stained with temporal punishment due to sins are purified after death. St. Cyprian (died 258) taught that penitents who die before the Sacrament of Penance must perform the remainder of any atonement required in the other world, while martyrdom counts as full satisfaction (Epistola 55, 20). St. Cyril of Jerusalem (315-386) described the sacred rites of the Liturgy with the comment, "Then we pray also for the dead, our holy fathers, believing that this will be a great help for the souls of those for whom the prayer is offered" (Catechesis, 32).
St. Augustine not only presumed the existence of purgatory as a matter of divine faith, but also testified to this belief from the Scriptures. Among other statements, he said, "some believers will pass through a kind of purgatorial fire. In proportion as they loved the goods that perish with more of less devotion, they shall be more of less quickly delivered from the flames." He further declared that the deceased are "benefited by the piety of their living friends, who offer the Sacrifice of the Mediator, or give alms to the Church on their behalf. But these services are of help only to those lives had earned such merit that suffrages of this could assist them. For there is a way of life that is neither so good as to dispense with these services after death, nor so bad that after death they are of not benefit" (Enchiridion 69, 110).
Augustine's most beautiful tribute to purgatory occurs in the book of his Confessions, where he describes the death of his mother Monica and recalls her final request, "Lay this body anywhere at all. The care of it must not trouble you. This only I ask of you, that you remember me at the altar of the Lord wherever you are." Augustine complied with his mother's desire and admits that he did not weep "even in those prayers that were poured forth to Thee while the sacrifice of our redemption was offered for her" (Confessions, IX, 11).
After the Patristic period, the Church did not significantly develop the doctrine of purgatory for many centuries. Then in the twelfth century, Pope Innocent IV (1243-54), building upon the writings of the Fathers, expounded in detail upon the doctrine. In context, Innocent was concerned with reuniting the Greek Church which had been in schism since the Photian scandal in the ninth century. He appealed to the Greek's belief in a state of purgation as a point of departure from which to bring them into communion with Rome. In a doctrinal letter to the apostolic delegate in Greece, he discussed the common belief:
It is said that the Greeks themselves unhesitatingly believe and maintain that the souls of those who do not perform a penance which they have received, or the souls of those who die free from mortal sins but with even the slightest venial sins, are purified after death and can be helped by the prayers of the Church.
Since the Greeks say that their Doctors have not given them a definite and proper name for the place of such purification, We, following the tradition and authority of the holy Fathers, call that place purgatory; and it is our will that the Greeks use that name in the future.
For sins are truly purified by that temporal fire — not grievous or capital sins which have not first been remitted by penance, but small and slight sins which remain a burden after death, if they have not been pardoned during life (DB, 456).
