The question that saint Paul asks is "what are these people doing, who are baptised on behalf of the dead? If the dead cannot be raised, why do they want to be baptised for the dead?"
Baptism is both into Christ's death and into his resurrection. More to the point baptism is into union with Christ. It may be unwise to place too much emphasis on death when discussing baptism. But saint Paul is asking why people are baptised for the dead which is not a practise that any church (except Mormons) engages in today. So everybody is a little confused by what he wrote. It would be interesting to know but saint Paul didn't write any explanation. I am sure that the Corinthian Christians would have known. It may be that Christians in other cities also knew but the reasons for the practise have not been preserved either in writing or in traditions handed down through the centuries.
I have wondered at this passage as well, so I went to Chrysostom's commentary, and was astonished at what I found...
http://www.newadvent.org/fathers/220140.htm
John takes quite a bit of time approaching the passage, and I may have gotten it wrong, but as I am reading his commentary I think he is sayint that EVERY Baptism is for the dead... Which brings us right into the middle of Josiah's Lament about how Christ is the Savior and the dead cannot give Life to themselves... The dead one is being baptized for the one who is dead - eg for himself or herself... One enters into the Waters of Regeneration as a dead person, and emerges as one reborn of Spirit and Water... This is the difference between the Christian Saint and the Old Testament Saint, because while the OT Saints were far more righteous in their conduct, and far more saturated in the Holy Spirit of God - I mean, have you ever seen a face like that of Moses where one cannot bear to gaze upon it? - Yet these are still not re-birthed into the post-incarnate and Ascended Christ... They had not been Baptized into Christ... Yet they were Saturated in the Holy Spirit, talked with God, wrote prophetically, etc etc... Yet as Paul records in Hebrews, they were not perfected in God UNTIL Christ descended into hades after His Life-bestowing death on the Cross and brought them forth with us who ARE Baptized into Christ...
And if this take is right, and I think it is, then Josiah's Lament is answered in Scripture very elegantly, because it does not say that the Baptized are Baptized for the dead... Yet it is the dead who are Baptized into Life, without question... The Baptismal Waters are Scripturally called the Waters of Regeneration (Rebirth) and Christ IS the one Baptizing the dead into Life, into Himself, into His Body... For we in Him are become members of His Body, the Ekklesia, the Assembly of Christ called out from the world into the Kingdom of Heaven which is Christ...
The mistake in the Lament of Josiah is this IDEA that repentance is a Good work... Good has nothing too repent FROM... Christ Himself did not repent... ONLY evil is capable of repentance... Because repentance is denial of self in sin... We CAN say that it is a good thing to repent, and that is true, but it is not a work of the Good, but is only a work against evil in one's self... The most drooling beast
can turn from any particular evil it is contemplating... But it cannot give itself Life - Only God can give Life... But evil without God's Life CAN repent from evil, and CAN produce the Fruits of Repentance, while still dead in its treaspasses...
In fact, even after the Rebirth of Baptism into Christ, the body is still dead in its treaspasses, which still clamor for their fulfillment because of long habits... And keeping the purity of soul and body in the face of this clamor and that of the persecutions of the world is the "running of the race set before us" that Paul enjoins us to engage against demonic powers...
And we cannot Baptize ourselves... Only the body of Christ can Baptize the Dead into Life... Because only Christ HAS the Life that the Dead do not have but need so urgently...
Christian Life is man's uest for God in all thingns...
Arsenios
The absence of "baptism for the dead" in Christian Tradition and in written records from the churches is testimony that whatever the practise was it was not essential to Christian living and teaching. It did not endure because it was not worth retaining.