Some background: what Purgatory is, and what it is not
Before answering the question, it is necessary to understand exactly what the Church means by “Purgatory.” The Catechism of the Catholic Church (CCC) says the following:
1030. All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.
1031. The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire:
As for certain lesser faults, we must believe that, before the Final Judgment, there is a purifying fire. He who is truth says that whoever utters blasphemy against the Holy Spirit will be pardoned neither in this age nor in the age to come. From this sentence we understand that certain offenses can be forgiven in this age, but certain others in the age to come [a quotation from St. Gregory the Great, Dial. 4,39:PL 77,396, with a reference to Mt. 12:31].
Hence, Purgatory is a temporary state that allows souls that die in friendship with God, and yet are still have some of the effects of sin in their soul, to be cleansed before their definitive encounter with God. This cleansing (which may take place on earth, in the form of reparation, or after death in Purgatory) constitutes the “temporal punishment” that is is the consequence of committing offences against God.
It is absolutely not, therefore, a “miniature Hell,” nor is it an intermediate state “between” Heaven and Hell. All souls in Purgatory are assured of their salvation; they are guaranteed to be in Heaven one day.
The Church teaches that it is the duty and a work of mercy for Christians to pray for the souls being cleansed after death—and this is the justification for indulgences (remittance of the temporal punishment due to sin) that are applied to the deceased (see CCC 1032).
Many sources speak of a “purifying fire,” including the text from St. Gregory above, but we must stress that the “fire” in question is strictly metaphorical, since the persons in Purgatory are still waiting for the Resurrection of the Body. (Hence the fanciful depictions of Purgatory in works such as the Purgatorio in Dante’s Divine Comedy must be regarded as metaphorical, and often, as simply inaccurate.)
(Another common misconception is that persons spend a certain amount of “time” in Purgatory, and that the prayers and indulgences reduce or eliminate that “time.” This misconception has doubtless been fostered in part by the fact that before the current Enchiridion on Indulgences, indulgences were often given with a number of “days” or “years;” however, the time period was intended to indicate, not the amount of time remitted in Purgatory, but the duration of certain penances that were traditionally given back in the Middle Ages—indulgences were originally intended to be remissions of all or part of those penances. In fact, since the persons in Purgatory do not yet have bodies—having lost theirs at death and since they are awaiting General Resurrection—they do not experience time in the same way we do on earth. A more severe purification need not, therefore, take place over a longer period of “time.”)
Biblical basis for Purgatory
Although this question has been dealt with in What is the Biblical support for Purgatory?, for the reader’s convenience, here are the passages that the Church refers to:
First, there is 2 Macc. 12:39-45:
39 On the next day, as by that time it had become necessary, Judas and his men went to take up the bodies of the fallen and to bring them back to lie with their kinsmen in the sepulchres of their fathers. 40 Then under the tunic of every one of the dead they found sacred tokens of the idols of Jam′nia, which the law forbids the Jews to wear. And it became clear to all that this was why these men had fallen. 41 So they all blessed the ways of the Lord, the righteous Judge, who reveals the things that are hidden; 42 and they turned to prayer, beseeching that the sin which had been committed might be wholly blotted out. And the noble Judas exhorted the people to keep themselves free from sin, for they had seen with their own eyes what had happened because of the sin of those who had fallen. 43 He also took up a collection, man by man, to the amount of two thousand drachmas of silver, and sent it to Jerusalem to provide for a sin offering. In doing this he acted very well and honorably, taking account of the resurrection. 44 For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead. 45 But if he was looking to the splendid reward that is laid up for those who fall asleep in godliness, it was a holy and pious thought. Therefore he made atonement for the dead, that they might be delivered from their sin (RSV-CE).
It should be pointed out that Catholics (and Orthodox) regard 1 and 2 Maccabees to be part of the Canon of Scripture, whereas most Protestant denominations do not. Catholics and Orthodox, therefore, consider these books to be the inspired Word of God, and hence must accept clear teaching of doctrine, as in Verse 45, as binding. However, regardless of whether one considers the Books of the Maccabees canonical, they give clear evidence that mainstream Jews in the second century B.C.—at least those who accepted the Resurrection of the Body—routinely made prayers for the dead, a practice that doubtless passed into the early Church. Since prayers cannot help either those in Heaven (because they are already enjoying their definitive encounter with God) or in Hell (because they are eternally deprived of that encounter), it is reasonable to posit a state of purification that occurs after death, for those who need it before they enter Heaven.
Perhaps even clearer than 2 Maccabees is 1 Corinthians 3:12-15 (a text whose canonicity no mainstream Christian denomination disputes):
12 Now if any one builds on the foundation [i.e., Jesus Christ] with gold, silver, precious stones, wood, hay, stubble— 13 each man’s work will become manifest; for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each one has done. 14 If the work which any man has built on the foundation survives, he will receive a reward. 15 If any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire (RSV-CE).
St. Paul in this passage is speaking of the Day of the Lord: a reference to an image dear to many of the Old Testament prophets; in the Prophets, the Day of the Lord refers to moments when God enacts judgment: either on Israel itself, or on her enemies, or else (especially in the later prophets) the judgment that people will receive when they die, or else at the General Resurrection. Here, clearly Paul means the judgment that people will receive after death.
Paul teaches that after death each person’s works (meaning the actions and habits that each person has done during his life) are tested by fire. Those that are enduring (those done in cooperation with the grace of God) survive the test; those that are not (the lingering effects of sinful acts, or acts done without the help of God’s grace) will perish.
It should be noted that this test by fire is not the same as the judgment that determines whether a person will go to Heaven or to Hell: Paul is clearly speaking of those who “will be saved,” although for those with works of straw, “as through fire.” These are all persons who have died in friendship with God, some of whom, however, need a cleansing of their works of straw before they are saved (that is, before they make their definitive encounter with God).
The passage from 1 Corinthians is by far the most explicit; there is also Mt. 5:25-26:
25 Make friends quickly with your accuser, while you are going with him to court, lest your accuser hand you over to the judge, and the judge to the guard, and you be put in prison; 26 truly, I say to you, you will never get out till you have paid the last penny (RSV-CE).
This passage is not, of course, a definitive proof of the existence of Purgatory, but that is certainly a possible interpretation. Coming, as it does, in the Sermon on the Mount, it lends itself to a reflection on the judgment after death. The allegory would be as follows: the time we have on earth is our journey to the courthouse; the “accuser” would be God; and the trial, the judgment we receive at death. We can “make friends” with God now, or else pay the “penalty” in “prison” (i.e., after death). Jesus seems to suggest that the “prison term” is finite—it only lasts as long as there is a “debt” to pay.
A historical argument
The early Christians were fiercely defensive of the true doctrine, and whenever a serious deviation was introduced, there was a swift reaction by those who maintained the orthodox view: this attitude is evident in the various controversies that arose in the first centuries: Marcion (who led a Gnostic sect), Sabelius (who advocated Modalism, a Trinitarian heresy), Arius (who denied the divinity of the Word), the “Pneumatomachoi” (who denied the divinity of the Holy Spirit), Nestorius (who denied the personal unity of Jesus), and so on—there are countless examples. We would expect that if the doctrine of Purgatory were seen as innovative and dangerous, that there would have been a vocal reaction on the part of the Church; however, there was not. The practice of praying for the dead was uncontroversial (and indeed predates Christianity, as we saw with the passage from 2 Maccabees), as was the idea that a purification is sometimes necessary before persons enter Heaven (already taught by St. Paul, as we saw).
On the contrary, no one, not even the leaders of “heretical” sects (Sabellians, Arians, Montanists, Novatians, and so on) seems to have doubted that idea, which explains why it is not dealt with systematically by the Fathers. Nevertheless, there is a continuous history of belief in such a purification and the need to pray for those persons undergoing it.
The Tradition regarding Purgatory
I reproduce some passages, which I have taken from the article “The Roots of Purgatory” by Catholic Answers.
Texts that bear witness to belief in Purgatory
The following texts are not by Church Fathers, but they bear witness to the fact that mainstream, orthodox Christians believed in a purification after death (i.e., Purgatory), as early as the second century A.D.:
And after the exhibition, Tryphaena again received her [Thecla]. For her daughter Falconilla had died, and said to her in a dream: ‘Mother, you shall have this stranger Thecla in my place, in order that she may pray concerning me, and that I may be transferred to the place of the righteous’ (Acts of Paul and Thecla [A.D. 160], emphasis added).
The citizen of a prominent city, I erected this while I lived, that I might have a resting place for my body. Abercius is my name, a disciple of the chaste Shepherd who feeds his sheep on the mountains and in the fields, who has great eyes surveying everywhere, who taught me the faithful writings of life. Standing by, I, Abercius, ordered this to be inscribed: ‘Truly, I was in my seventy-second year. May everyone who is in accord with this and who understands it pray for Abercius’ (Epitaph of Abercius [A.D. 190], emphasis added).
Here is a text from the Acts of the Martyrdom of Perpetua and Felicity, martyrs from the city of Rome itself.
[T]hat very night, this was shown to me in a vision: I [Perpetua] saw Dinocrates going out from a gloomy place, where also there were several others, and he was parched and very thirsty, with a filthy countenance and pallid color, and the wound on his face which he had when he died. This Dinocrates had been my brother after the flesh, seven years of age, who died miserably with disease. […] For him I had made my prayer, and between him and me there was a large interval, so that neither of us could approach to the other. […] and [I] knew that my brother was in suffering. But I trusted that my prayer would bring help to his suffering; and I prayed for him every day until we passed over into the prison of the camp, for we were to fight in the camp-show. Then […] I made my prayer for my brother day and night, groaning and weeping that he might be granted to me. Then, on the day on which we remained in fetters, this was shown to me: I saw that the place which I had formerly observed to be in gloom was now bright; and Dinocrates, with a clean body well clad, was finding refreshment, […] he went away from the water to play joyously, after the manner of children, and I awoke. Then I understood that he was translated from the place of punishment (The Martyrdom of Perpetua and Felicity 2:3–4 [A.D. 202], emphasis added).
Witnesses from Church Fathers and ecclesiastical writers
The first couple of texts are from Tertullian. He is not exactly a Church Father (he joined a rigoristic sect called the Montanists in the latter part of his life), but he is an important witness to the beliefs of the Church in the early third century A.D.
The first is from De corona (On the crown), which discusses martyrdom. In Chapter 3—which, interestingly, is a justification of the practices of Christians that are handed down as tradition—he notes that
As often as the anniversary [of a person’s death] comes round, we make offerings for the dead as birthday honours (De corona 3:3 [A.D. 211]).
He cites this as an example of something unobjectionable that has been a constant custom among Christians.
In a similar vein, in his De monogamia (On Monogamy), he says
Indeed, she [a Christian widow] prays for his [her husband’s] soul, and requests refreshment for him meanwhile, and fellowship with him in the first resurrection; and she offers her offering on the anniversaries of his falling asleep (De monogamia 10:5 [A.D. 216]).
Note that in this work Tertullian is excessively rigorous regarding matrimony, but the important thing for our purposes is that he is a witness to the fact that praying for the dead is unobjectionable, and the Christians believed that such prayers brought “refreshment” (refrigerium) to them.
Moving on to writers who are unquestionably Church Fathers, we have the following passage from Letter 51 of St. Cyprian of Carthage (who was, apparently, a pupil of Tertullian, although he rejected Tertullian’s rigorism and, evidently, never left communion with the Church). In his letter, St. Cyprian explains how it is possible for the Church to pardon apostates, adulterers, and others who have committed serious offences. It does not diminish the Church’s holiness, he argues, because she has re-admitted her lapsed sons; just as the Church is no less pure because some of her members have committed adultery and have been reconciled, neither is she less holy because she re-admits apostates and lapsi. In this context, he says,
It is one thing to stand for pardon, another thing to attain to glory: it is one thing, when cast into prison, not to go out thence until one has paid the uttermost farthing; another thing at once to receive the wages of faith and courage. It is one thing, tortured by long suffering for sins, to be cleansed and long purged by fire; another to have purged all sins by suffering. It is one thing, in fine, to be in suspense till the sentence of God at the day of judgment; another to be at once crowned by the Lord (Epistle 51:20 [A.D. 253], emphasis added).
Here, St. Cyprian describes the doctrine that we are familiar with: it is possible for a person to expiate all of his sins in this life, and hence attain the crown of glory immediately upon his death; others, however, are purified after death.
Saint Cyril of Jerusalem, the bishop of Jerusalem from about 350–386, in one of his catecheses to catechumens, explains the suffrages to the dead in the liturgy:
Then we make mention [i.e., in the Canon or Eucharistic Prayer] also of those who have already fallen asleep: first, the patriarchs, prophets, apostles, and martyrs, that through their prayers and supplications God would receive our petition; next, we make mention also of the holy fathers and bishops who have already fallen asleep, and, to put it simply, of all among us who have already fallen asleep, for we believe that it will be of very great benefit to the souls of those for whom the petition is carried up, while this holy and most solemn sacrifice [i.e., the Divine Liturgy] is laid out (Catechetical Lectures 23:5:9 [A.D. 350], emphasis added).
In a sermon, Saint Gregory of Nyssa, one of the Cappadocian Fathers renowned for defending the divinity of the Holy Spirit and helping to formulate the Trinitarian dogmas in their present form, explains that those who have not led a life of virtue (especially, letting their passions dominate rather than reason), and yet is in friendship with God, will experience a purification after death:
If a man distinguish in himself what is peculiarly human from that which is irrational, and if he be on the watch for a life of greater urbanity for himself, in this present life he will purify himself of any evil contracted, overcoming the irrational by reason. If he has inclined to the irrational pressure of the passions, using for the passions the cooperating hide of things irrational, he may afterward in a quite different manner be very much interested in what is better, when, after his departure out of the body, he gains knowledge of the difference between virtue and vice and finds that he is not able to partake of divinity until he has been purged of the filthy contagion in his soul by the purifying fire (Sermon on the Dead [A.D. 382], emphasis added).
St. John Chrysostom, the renowned bishop and orator of Constantinople, in a homily on 1 Corinthians, teaches that offerings for the dead bring them consolation:
Let us help and commemorate them. If Job’s sons were purified by their father’s sacrifice [Job 1:5], why would we doubt that our offerings for the dead bring them some consolation? Let us not hesitate to help those who have died and to offer our prayers for them (Homilies on First Corinthians 41:5 [A.D. 392]).
Moreover, he explains in a homily of Philippians that there is the possibility of removing the residual effects of sin in this life. Nevertheless, for those who did not take advantage of that possibility, those still on earth can bring consolation to the deceased by offering prayers and giving alms:
Weep for those who die in their wealth and who with all their wealth prepared no consolation for their own souls, who had the power to wash away their sins and did not will to do it. Let us weep for them, let us assist them to the extent of our ability, let us think of some assistance for them, small as it may be, yet let us somehow assist them. But how, and in what way? By praying for them and by entreating others to pray for them, by constantly giving alms to the poor on their behalf. Not in vain was it decreed by the apostles that in the awesome mysteries [i.e., the Divine Liturgy, or celebration of the Eucharist] remembrance should be made of the departed. They knew that here there was much gain for them, much benefit. When the entire people stands with hands uplifted, a priestly assembly, and that awesome sacrificial Victim is laid out, how, when we are calling upon God, should we not succeed in their defense? But this is done for those who have departed in the faith, while even the catechumens are not reckoned as worthy of this consolation, but are deprived of every means of assistance except one. And what is that? We may give alms to the poor on their behalf (Homilies on Philippians 3:9–10 [A.D. 402], emphasis added).
It is interesting to note that St. John Chrysostom attributes the celebration of the mysteries (that is, of the Eucharist) for the sake of the departed to the authority of the apostles: this is evidence of an unwritten tradition that is recorded for the first time in Chrysostom’s day. (This one passage is not, of course, enough to prove the direct link to the Apostles, but the continuous existence of the belief and practice cannot be doubted.)
Finally, there are the works of St. Augustine, the bishop of the northern African town of Hippo from 395-430, the first Father to formulate the doctrine of Original Sin.
He explains in a sermon that prayers are not offered on behalf of the martyrs (because they presumably never needed to be purified after death); however prayers are offered for the sake of the other dead:
There is an ecclesiastical discipline, as the faithful know, when the names of the martyrs are read aloud in that place at the altar of God, where prayer is not offered for them. Prayer, however, is offered for other dead who are remembered. It is wrong to pray for a martyr, to whose prayers we ought ourselves be commended (Sermons 159:1 [A.D. 411]).
In a different sermon, explains that prayer and almsgiving on behalf of the dead bring them aid. He affirms that prayers and liturgical actions for the sake of the dead are a universal practice in the Church, and that the practice is already an old tradition (“from the Fathers”):
But by the prayers of the holy Church, and by the salvific sacrifice [i.e., the celebration of the Eucharist], and by the alms which are given for their spirits, there is no doubt that the dead are aided, that the Lord might deal more mercifully with them than their sins would deserve. The whole Church observes this practice which was handed down by the Fathers: that it prays for those who have died in the communion of the Body and Blood of Christ, when they are commemorated in their own place in the sacrifice itself; and the sacrifice is offered also in memory of them, on their behalf. If, then, works of mercy are celebrated for the sake of those who are being remembered, who would hesitate to recommend them, on whose behalf prayers to God are not offered in vain? It is not at all to be doubted that such prayers are of profit to the dead; but for such of them as lived before their death in a way that makes it possible for these things to be useful to them after death (Sermons 172:2, emphasis added).
He explains in his City of God that only those who have not been purified in this life must be purified in the next. He also affirms that not all punishment after death is eternal; there is a temporal punishment, or purification:
Temporal punishments are suffered by some in this life only, by some after death, by some both here and hereafter, but all of them before that last and strictest judgment. But not all who suffer temporal punishments after death will come to eternal punishments, which are to follow after that judgment (De civitate Dei 21:13 [A.D. 419]).
In what is probably the first use of the term purgatorium (“cleansing”)—and probably the source of the term Purgatory in the Middle Ages—Augustine affirms that some of the faithful are saved through a “cleansing fire.” (Augustine doubtless had in mind the passage from 1 Corinthians quoted above.)
That there should be some fire even after this life is not incredible, and it can be inquired into and either be discovered or left hidden whether some of the faithful may be saved, some more slowly and some more quickly in the greater or lesser degree in which they loved the good things that perish, through a certain purgatorial fire (per ignem quemdam purgatorium) (Handbook on Faith, Hope, and Charity 18:69 [A.D. 421]).
Note how St. Augustine uses fire in a strictly metaphorical sense, as do all the Fathers. A little later on, Augustine explains further, and as can be seen all the elements of the modern doctrine of Purgatory are in place: the fact the some persons die in friendship with God, but not perfectly purified (and that it is, is however, possible to be purified completely in this life); the possibility of purification after death; and the necessity to pray and make offerings for the dead, both personally and in the Liturgy (especially the celebration of the Eucharist, what Western Catholics call the Mass):
The time which interposes between the death of a man and the final resurrection holds souls in hidden retreats, accordingly as each is deserving of rest or of hardship, in view of what it merited when it was living in the flesh. Nor can it be denied that the souls of the dead find relief through the piety of their friends and relatives who are still alive, when the Sacrifice of the Mediator [i.e., the celebration of the Eucharist] is offered for them, or when alms are given in the Church. But these things are of profit to those who, when they were alive, merited that they might afterward be able to be helped by these things. There is a certain manner of living, neither so good that there is no need of these helps after death, nor yet so wicked that these helps are of no avail after death (Handbook on Faith, Hope, and Charity, 29:109).
If we add to this the witness of one of the last Western Fathers, St. Gregory the Great, quoted above in the text from the Catechism, it seems impossible to deny that belief in the doctrine of Purgatory has been present in the Church from the beginning, and in every part of the Church, both Eastern and Western. (It acquired the name “Purgatory” only in the Middle Ages, but the belief was there all the same.)
The Church would argue that there is a very strong argument for Purgatory from Tradition. The Scripture is not very explicit, but neither does it contradict the doctrine, and there are several important passages that support it: most notably 1 Corinthians 3:12-15. Although the Bible is not perfectly clear on this point, there is evidence of belief in a purification of the deceased after death among the Israelites at the time of the Maccabees, and of universal belief in Purgatory (though not, of course, by that name) among Christians from at least the second century A.D. The historical record shows that such a belief has been continuous to the present day, and that it was fundamentally uncontroversial until the late Middle Ages (when there began to be disputes with the Eastern Orthodox over the precise meaning of the term “Purgatory” and what sort of punishment it entailed).