1) "If Jesus Christ died ‘once for all,’ why then do you Catholics think you need to suffer in purgatory for your sins?" (Hebrews 7: 27; 9: 27-28; 10: 10) – Purgatory has nothing to do with salvation. Rather, it is part of the preparation of the saved who are about to enter into the joys of eternal life. Purgatory is God’s way of eliminating the temporal effects due to sin, but it has no connection with the eternal penalty (hell) merited by our sin.

2) Purgatory is not a place where the soul works or earns or in any way does something to cleanse himself — all purification that takes place in purgatory is done by God to the soul – "Too pure are your eyes to look upon evil O Lord, and the sight of misery you cannot endure" (Habakkuk 1: 13).

3) Purgatory is not a third option for where you end up after you die; there is no such thing as a "middle ground" when it comes to salvation –there are only two ultimate options, heaven and hell (Matthew 25:31-46). It must be understood as simply a part of the process for some souls who are destined for heaven

Matthew 18:32-35 – God does not literally lock us away…so there must be somewhere that this debt is repaid. The debt we call the "temporal punishment due to sin" (see below) and the place we call Purgatory

1 Peter 3: 18-19; 4:6 – these "souls in prison" cannot be referring to the "Limbo of the Fathers" (where all the just waited until Christ re-opened the gates of Heaven to man), so it must be referring to someplace else.

2 Maccabees 12:43-45 – there is no hope or release for the souls in Hell, so there is no reason to pray for them…which means that the dead in this passage cannot be there; the souls in Heaven do not require anyone to pray for them; therefore, they must be somewhere that is neither Heaven or Hell but where the prayers of the living assist them

Luke 16:19-31 – the dead interceding for the living; the souls in Hell have no charity to do so nor the ability to do so; Dives was not in Heaven (the "bosom of Abraham") and so he had to be in another place.

Also, very importantly, the scriptural texts as they stand say nothing whatsoever that would exclude purgatory. They are not saying that after death the saved person goes immediately to heaven. Purgatory is quite compatible with these passages (when they are quoted correctly, of course).

The eternal penalty due to sin is hell, but that is distinct from the other, inevitable, penalty that arises when we sin: the aftereffects that play out across space and time.

When Adam and Eve committed the "original sin" in the Garden (cf. Gen. 3:1-7), they disrupted their intimate friendship with the Lord. When they fell from grace, they lost their many supernatural gifts of grace and union with God, and they lost many of their natural gifts, such as freedom from their passions, control over their will, and a preternaturally enhanced human knowledge. Their gift of immortality was taken away. And with that loss came a series of other "temporal punishments," consequences of their sin, that continue, embedded in the human condition, down to our own day.

But we also see that, following on the heels of their spiritual death came a series of natural consequences that also spelled death for humanity and all creation:

Adam and Eve were forgiven of their sin, and the eternal penalties of that sin, for them and all the rest of humanity that repents and asks forgiveness, is eliminated by Christ’s death on the cross. But the suffering and temporal effects due to sin sickness, anguish, death remain (cf. CCC 1008, 1472, 1505).

This principle of a separate temporal punishment due to sin is seen throughout the Bible. (2 Sam. 12:7-14; cf. Num. 12:1-15, 22:12, 27:12-14).

Tertullian, A.D. 216 — "A woman, after the death of her husband ... prays for his soul and asks that he may, while waiting, find rest; and that he may share in the first resurrection. And each year, on the anniversary of his death, she offers the sacrifice" (On Monogamy 10:1-2).

Lactantius, A.D. 307 — "But also, when God will judge the just, it is likewise in fire that he will try them. At that time, they whose sins are uppermost, either because of their gravity or their number, will be drawn together by the fire and will be burned. Those, however, who have been imbued with full justice and maturity of virtue, will not feel that fire; for they have something of God in them which will repel and turn back the strength of the flame" (Divine Institutes 7:21:6).

St. Cyril of Jerusalem, A.D. 350 — "Then we make mention 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 is laid out" (Catechetical Lectures 23:5:9).

St. John Chrysostom, A.D. 392 — "Let us help and commemorate them. If Job’s sons were purified by their father’s sacrifice,[25] 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 1 Corinthians 41:5).

St. Augustine of Hippo — "But by the prayers of the Holy Church, and by the salvific sacrifice, 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" (ibid., 172:2).

If A) nothing impure can enter God’s presence (remember Habakkuk 1: 13 ?); and B) you can only go to one of two places when you die (that is, Heaven or Hell)

Then it follows that either 1) everyone is perfectly good when they die or they have completely severed their relationship with God or 2) those who have no completely severed their relationship with God but who are not perfectly good when they die must be purified before entering the presence of God.

We reject 1 because: those people who do not completely sever their relationship with God do not die perfectly good; we also believe in temporal punishment (a Biblically sound teaching). Therefore, it must be 2.

The devotion began from the diary of a young Polish nun, Saint Faustina Kowalska, describing apparitions she had of our Lord and reminding the faithful of what the Church has always taught: that God is merciful and forgiving and that we, too, must show mercy and forgiveness.

The message of mercy is that God loves us — all of us — no matter how great our sins. He wants us to recognize that His mercy is greater than our sins, so that we will call upon Him with trust, receive His mercy, and let it flow through us to others.

– see http://www.envoymagazine.com/planetenvoy/Special-PurgatoryEmergencyRoom1.htm