"Baptism for the Dead" 1 Corinthians 15:29
There were certain false teachers among the Corinthian believers who claimed that the resurrection had ALREADY taken place and that there was no further resurrection that was going to take place at the end of the world. Paul was rebutting this fallacy by assuring the Corinthian believers that there most certainly will be a future resurrection and that all who believe, including those who had died in the faith, would be in this yet future blessed resurrection.
This phrase in 1 Corinthians 15:29,
"Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?", can be paraphrased "or else what will happen to the dead believers who have been baptized? (If the dead raise not in the resurrection). Why (concerning the dead believers) have they been baptized?"
The point Paul is making is that if the dead rise not, then those dead Christians who were baptized while they were alive were baptized in vain and have no hope. The fact that this is the point that Paul is making becomes very evident when one considers the entire context of the verse by reading the entire chapter 15 from verse 12 and onward.
Point #1. 1 Cor 15:12
"Now if Christ be preached that He rose from the dead, HOW SAY SOME AMONG YOU THAT THERE IS NO RESURRECTION OF THE DEAD? 13 But if there be no resurrection of the dead, then is Christ not risen:"
From this verse we see Paul make his opening point of the discussion. Paul is calling attention to the FALSE TEACHERS who are teaching that the resurrection is past already.
Point #2. 1 Cor 15:14
"And if Christ be not risen, then is our preaching vain, and your faith is also vain. 15 Yea, and we are found false witnesses of God; because we have testified of God that He raised up Christ: whom He raised not up, if so be that the DEAD rise not. 16 For if the DEAD rise not, then is not Christ raised: 17 And if Christ be not raised, your faith is vain; ye are yet in your sins. 18 Then they also which are FALLEN ASLEEP in Christ are perished. 19 If in this life only we have hope in Christ, we are of all men most miserable."
Here Paul assures the believers that because Christ has in fact arisen and those who have fallen asleep have not perished and their hope is NOT in this life only.
Point #3. 1 Cor 15:20
"But now is Christ risen from the dead, and become the firstfruits of them that slept. 21 For since by man came death, by man came also the resurrection of the dead. 22 For as in Adam all die, even so in Christ shall all be made alive. 23 But every man in his own order: Christ the firstfruits; afterward they that are Christ's at His coming. 24 Then cometh the end, when He shall have delivered up the kingdom to God, even the Father; when He shall have put down all rule and all authority and power. 25 For He must reign, till He hath put all enemies under His feet. 26 The last enemy that shall be destroyed is DEATH. 27 For He hath put all things under His feet. But when He saith all things are put under Him, it is manifest that He is excepted, which did put all things under Him. 28 And when all things shall be subdued unto Him, then shall the Son also Himself be subject unto Him that put all things under Him, that God may be all in all."
Paul is stating here that at Christ's coming all believers in Christ who have died as the result of Adam's sin will partake of the gift of eternal life when they are raised up on the last day and the last enemy, death, shall be destroyed and all things in nature will be put once again under the subjection of God's will, including Christ Himself.
Point #4. 1 Cor 15:29
"Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead? 30 And why stand we in jeopardy every hour? 31 I protest by your rejoicing which I have in Christ Jesus our Lord, I die daily. 32 If after the manner of men I have fought with beasts at Ephesus, what advantageth it me, IF THE DEAD RISE NOT? Let us eat and drink; for tomorrow we die. 33 Be not deceived: evil communications corrupt good manners. 34 Awake to righteousness, and sin not; for some have not the knowledge of God: I speak this to your shame."
Paul here rebukes the Corinthians for sinning by listening to these false teachings and falling away from the hope and assurance of the resurrection for ALL who believe, both the living and the dead. Thus the phrase, "Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?" Meaning: In light of all that Paul has stated, he asks, "Or else, concerning the dead (hyper ton necron), what shall they do which have been baptized. If the dead rise not at all?" These false teachers were teaching that only those who are alive at the coming of Christ will be saved and given eternal life and that those baptized believers who have died will not be raised and not have eternal life because the resurrection has already passed.
These verses take on very clear meaning once one translates "hyper" as "concerning" rather than "for" as the KJV does. Paul's discussion is "concerning those baptized who have died" to translate it as "baptized for the dead" adds needless confusion and some wish to infer from this poor translation that the early church was baptizing living people in behalf of those dead relatives and friends who were never baptized while they were alive. This is what the Mormons are attempting to practice, but once one translates Paul correctly, this practice is easily recognized as ridiculous.