I was reading across this board and one Fr. Averky gave an interesting answer that you may want to pose to your uncle:http://www.monachos.net/forum/archive/index.php/t-1609.html
He says:You have been given some well-researched answers by others, and I hope that this will help to answer your question. Unlike Western Christianity, the Orthdodox church tends much less to "dogmatize" when it come to questions such as yours. The Western churches have more of a tendency to put everything into a neat, orderly and logical package. If you were to get to know Orthodoxy well, you would would find that to our Western counterparts, we seem to be a total mess, yet we seem to be very comfortable with our Christianity, and having very much the sense of being God's children, we leave much to the Mystery who is God. This is a simplistic answer, but it is true
The average Orthodox Christian does not concern himself if he might be "predestined" or not, and he certainly does not and could not have a notion of receiving salvation whether he wanted it or not ( Irresistable Grace) as is Calvin's idea. Nor could he imagine that if he was not among the Elect, that no matter how much he tried he would still be among the damned, again, Calvin's notion. The life of the Orthodox Christian is seen as a steady progression on the path to salvation, which is accomplished, by tears, sorrows and repentance and has as an impotant basis, love for God and neighbor, A perfect example of the Christian life is the parable of the Publican and the Pharisee, for the Pharisee is most of us, proud, uncaring and unloving for others, feeling "justified" in our small efforts, and looking down on the "low-lifes", the sinners of this world. He is a "good person," paying his taxes, never breaking the law, faithful to his wife and supportive of the governement. On the other hand, the Publican stands way in the back of the synagouge, and striking his breast, can only beg for God's mercy, and as Christ Himself tells us, it is his prayer which justified him and is plessing to God, for he is sincere and acknowledges that he is a sinner. If we live our lives in a Christian manner, we need not concern ourselves if we be among the elect or not. In the long run of things, Christ has come again, He has judged the living and the dead, and we have either reached salvation or condemned ourselves, but that is in the framework of eternity, so we still toil in this life and in the time God has given us. may we use it well.
I think that very well puts the Orthodox Christian position into perspective. I understand how hard it is to deal with Calvinists. I had an orthodox Presbyterian friend who was on fire. We would always get into heated arguments - whew!
As for praying for the reposed, point out to your uncle that his rejection of praying for the dead is a rather recent innovation. If we consult most of the components of Holy Tradition, we find in Liturgies, Scripture, and writings of the Church Fathers exhortations and prayers for them. Here are some examples:
From the ancient Syrian Liturgy of St. James, it says: "we commemorate all the faithful dead who have died in the true faith...We ask, we entreat, we pray Christ our God, who took their souls and spirits to Himself, that by His many compassions He will make them worthy of the pardon of their faults and the remission of their sins"
Furthermore, early Christian inscriptions demonstrate how this practice finds its roots in the early church. For instance, you find what are called "acclamatory" prayers addressed to those who have died, not directly to God, wishing for them some benefit. But then there are also formal prayers addressed to a person of the Godhead or an angel asking again for a type of benefit.
Point out, also, to your uncle that John Calvin acknowledged that it was a faith of the ancient church, albeit still condemning it. "For over thirteen hundred years it was the approved practice to pray for the deceased. All ancients fell into error; it was something human and therefore what they did must not be imitated." (Institutes of the Christian Religion, 3,5,10).
We understand that after death, the soul endures through the experience of purification and through our prayers, brought closer to God. We don't define "purgatory" and tend to stay away from the rather papistic, legalistic tendancies. However, this is all assuming that we're coming from this stern, worldly Calvinist perspective on death itself. Those who have reposed are not just simply dead bodies, because our God is the God of the Living. This seems to be a big stumbling block for Protestants approaching Orthodox perspectives on the grave (such as veneration of relics, praying for the repose, etc. etc.)
Hopefully that helped some. Keep us posted on what more your uncle has to say!
Peace be with you on your journey,