Q - Okay, so what is the deal with Purgatory?
A - Thanks for the question. First let me tell you what Purgatory is not. Purgatory is not heaven or hell. Purgatory is not a permanent state of being. Purgatory is not a "second chance" after we die to get it right. Purgatory is not how we "earn our way to heaven". Purgatory is not saying that Christ's sacrifice was insufficient.
So, now that we have that out of the way, we can go on to the doctrinal aspects of it. We will start with what the Church says about it.
In the Catechism of the Catholic Church it states 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.606 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:607
1032 This teaching is also based on the practice of prayer for the dead, already mentioned in Sacred Scripture: "Therefore [Judas Maccabeus] made atonement for the dead, that they might be delivered from their sin."609 From the beginning the Church has honored the memory of the dead and offered prayers in suffrage for them, above all the Eucharistic sacrifice, so that, thus purified, they may attain the beatific vision of God.610 The Church also commends almsgiving, indulgences, and works of penance undertaken on behalf of the dead:
- 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.608
- Let us help and commemorate them. If Job's sons were purified by their father's sacrifice, 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.611
- So, from the Church's own official documents we can see that Purgatory is the "final cleansing" of sin that we commit while on earth. This is because as Revelation 21:27 says, "nothing unclean shall enter" into heaven. If we are not perfect, and I haven't met a perfect person yet, and yet still merit (by God's grace alone) heaven, then we need to go through this purgation before entering into glory.
Some also say that it is unbiblical. While the word "purgatory" may not be in the Bible, there are certain passages that implicitly contain the basis of purgatory.
Matt 5: 25-26 says,
"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; truly, I say to you, you will never get out till you have paid the last penny."--Here we are being told that we will ultimately be held responsible for all of our actions. There are two dimensions to being forgiven for a sin, the divine and the human. While we may be forgiven by God, we still have to go to our brother for forgiveness as well. Here it says that if we fail to obtain the human dimension of forgiveness, then God will hold us responsible ultimately. But, the human element does not merit eternal, but rather finite, punishment. So, it leaves open the door to Purgatory, which is finite.
Next in 1 Corinthians 3:11-15 Paul writes,
"For no one can lay any foundation other than the one already laid, which is Jesus Christ. If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw, his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man's work. If what he has built survives, he will receive his reward. If it is burned up, he will suffer loss; he himself will be saved, but only as one escaping through the flames."--Paul is saying that we will not enter into our reward until we are cleansed of all unrighteousness. Clearly Paul says we will be "saved", but there will be loss and flames through which one escapes. Also, this loss will be for those things which are not of value.
Lastly, in 2 Maccebees 12 we see the practice of Jews offering up sacrifices for the dead. They would not do those in heaven or hell any good, so the passage at least points to the Jewish beliefs in some other state of being in the afterlife.
With all of this evidence we couple some ancient Christian statements on Purgatory and the evidence seems pretty weighty.
Here is another link if this short intro didn't fully answer your question.