I believe that since we are ALL part of the Body of Christ (Church Militant, Suffering, and Triumphant) and death cannot separate us from Christ or the Body, we CAN ask for the intercessionary prayers of the souls in Purgatory.
I have a Catholic relative who prays to her deceased father for intercession. (A good man, but obviously not Canonized.) Based on your whole post, I take it then, that I have no need to "correct" her as a Catholic. She also believes that her father is watching over her family and is thus aware of what is happening on earth. Is this correct?
Please forgive my ignorance, but I don't know anything of the exact Church teaching of purgatory. Who goes there? Why? What's it like, and for how long? What is the strongest scriptural support for this, or is this considered tradition?
You are correct. The "sense of the faithful" is active in your Catholic relative! Certainly, we must both agree that our love will be even greater in heaven - and nothing can separate us from the love of Christ. Thus, her father remains part of the Body and even more deeply desires her daughter's salvation and God's graces to rain upon her. I believe this is a comforting doctrine for those who have lost a loved one. A connection still remains between the two as a result of their love. (which is from Christ)
Please forgive my ignorance, but I don't know anything of the exact Church teaching of purgatory. Who goes there? Why? What's it like, and for how long? What is the strongest scriptural support for this, or is this considered tradition?
What Purgatory is I can tell you from the top of my head, but more Scriptural/Tradition quotes will have to await written sources that I don't have with me. Even several hundred years before Christ, Jews believed (at least Pharisees) that the souls of faithful men who had deviated somewhat from God's ways were subject to a third state of existence. Maccabees 12 talks about some men who died in battle with some amulets with them. Judas, the leader, took up a collection of money and sent it to the Temple and the men prayed for the souls of these men who died with the taint of idolatry on their hearts. The Scripture itself explains that there would be no point in praying for these men if they were in hell or heaven. Jesus also implies the existence of a third state between heaven and hell, as does Paul. Being that the first Christians were Jews of the Pharisaical branch, it would follow that they had similar beliefs as laid out in Maccabees. Practices noted in later writings show the validity of the teaching.
The idea is that nothing impure shall enter heaven. We must attain holiness - how can we come into union with God and not be holy ourselves? Before I continue, be advised that this is not holiness we attained ourselves, but through God's graces throughout our lives. When we are judged, God will note whether we have purified ourselves in this life. Is it possible we can attain union with God but have pride? Have sloth or vanity? Hardly! We must become like Christ to rise with Christ. Purgatory is a great mercy, because it gives us, the saved, a final opportunity to prepare ourselves for eternal life. We do NOT merit in Purgatory. It is a purging - which entails suffering (just like any purging or sacrifice does). But we know that we are destined for heaven. We will deeply desire to be purged of anything that keeps us from Christ. It is the result of Christ's work of redemption on the cross.
The Church doesn't officially teach much about Purgatory's means of punishment, or "length of time" spent there, and so forth. Private revelations given to others give us an indication that it would be better to be purged here on earth! But these are not part of the Deposit of Faith. The Scriptures and Apostolic Tradition don't teach us such things. So all we can do is speculate on the particulars.
Let me know if you want more specific Scripture/Tradition quotes.
Regards
Both Orthodox and Catholic believe that upon death few souls are ready to enjoy the vision of God, so called beatific vision and the highest state of happiness, to which we refer as Heaven or Paradise. We both believe that there is an intermediate state after death and then two possible final states, Heaven or Hell. We both believe that prayers should be offered for the repose of the souls of the dead, and that for those in an intermediate state these prayers have a salutary effect.
The Catholics believe that Christ judges everyone in so-called particular judgement immediately after death and if the soul is condemned to Hell, that is where it goes right away. If the soul is judged saved for eternal life, its final destination is heaven. However, most souls are burdened by the aftereffects of sin, even though that sin is forgiven them. The analogy is that even though a tumor has been removed from a sick man (=sin pardoned), the scar where the surgery took place needs to heal before the man can walk again (=be in the presence of God). That convalescence or purification happens in Purgatory. One mark of a saint is that he or she has completed the purification on earth in his lifetime and can go directly to heaven. The prayer is only efficacious for souls in purgatory, but not knowing who ends up where and at what time, we pray for all dead (a public mass for the dead is not allowed in cases of hardened public sinners, but private prayers are always a good thing).
The Orthodox beliefs are somewhat different. Both the condemned and the saved go through a process of trial, when Satan and Christ bargain for the soul. This is when we pray for them. The Orthodox do not use the word purgatory and consider the Catholic doctrine an innovation. I don't think they would say that our belief is definitely wrong, but it is not officially taught by the Orthodox Church.
You may be interested in some in-depth discussion I recently had with the Orthodox so that we understand each other better: Indulgences: Spreading the Wealth. I did not intend it as a vehicle for polemics witht he Protestants and you will see that I avoid arguing the scriptural basics there.
It is true that the doctrine of Purgatory, even its Orthodox less detailed counterpart is in some part speculative theology, in some part tradition that was written down by the Church fathers but never made it into the New Testament proper, and in some part scripture. I showed you why the Catholic theology of the afterlife is compatible with the scripture, but I agree that different interpretation of the same scripture is possible. Certianly the Orthodox interpretation is possible even though it differs from ours. I don't think that any interpretation of the scripture that denies the existence of an intermediate stage following death is possible though; at least I have not seen a satisfying exegesis of the parable of Unmerciful Debtor that would deny that a temporal punishment after death exists for some people.