Question: Is Mormon Practice of Vicarious Baptism for the Dead Biblical?
Question: Someone wrote, “While speaking to a Mormon who had just finished his two-year mission about our differences, one thing he mentioned was baptism—specifically I Corinthians 15:29. Mormons really believe in vicarious baptism, which obviously has no biblical standing—except for that verse. What is the Christian interpretation concerning this verse and what does it mean?”
1 Cor. 15:29 (NASB): “Otherwise, what will those (NKJV: they) do who are baptized for the dead? If the dead are not raised at all, why then are they baptized for them?”
 One use for the massive genealogical database (in the billions) that the Mormon Church has developed is for its members to get baptized for their dead relatives who weren’t Mormons in life.
Response: We can handle this verse in two ways.
First: Notice that apostle Paul uses 1st person pronouns “we” and “our” in 1 Cor.15:3, 14, 15, 19. and 2nd person plural pronoun “you” and “your” (p)—humeis, humin, humōn in Greek—in vv. 1, 3, 11, 14. The lone exception is v. 29 in which the pronoun changes to the 3rd person plural “they” (poiēsousin). Now, whenever pronouns “we” and “our” are used in the epistles, it refers to the true Christian body; so, when Paul uses these pronouns here, he is not referring just to himself and the Corinthian believers. Then, who are “they”?
At this point, examining 1 John 2:19 (ESV) is helpful because it contains the pronouns “we” and “they.” Apostle John writes, “They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us.” Here, John refers to people (“they”) who used to worship the Lord with him and other believers (“us”), but were no longer with “us,” both physically and doctrinally, because they opted for “docetism”—an erroneous Christology that saw Jesus as a spiritual entitty without flesh (1 Jn. 4:2-3). The pronoun “we” represents the Christian community while “they” represents those who were seemingly part of the proto-orthodox group (since orthodoxy as we understand it wouldn’t be officially promulgated until later centuries) but ultimately weren’t saved (2 Jn.1:9). In light of this, it can be reasoned that Paul’s use of “they” in 1 Cor. 15:29 refers to a group that claimed to be proto-orthodox Christians but ultimately weren’t, shown by their practice of vicarious baptism for the dead, a practice that he wouldn’t have endorsed.
Nevertheless, it is evident that the apostle doesn’t use strong language to condemn this practice. Why? Obviously, this group must have been well-known to the Corinthians because of its peculiar practice, for Paul abruptly mentions it without identifying them (perhaps by name) in the middle of his discourse. Had Paul been writing about the theological merit of vicarious baptism, he should have expounded on it further (unless the Corinthians were already familiar with the apostle’s position); however, his sole interest in 1 Corinthians 15 is to affirm the future resurrection of the believers on account of Christ’s physical resurrection. And since those who erroneously practiced vicarious baptism for the dead did so because they, at least, believed in the resurrection of Christ, Paul was merely using that to further buttress his point. It is as if the apostle were saying, “If those who get baptized for the dead do so because they believe in resurrection, how much more should you—the true Christians—believe it!”
It is akin to pastors talking positively about the hardworking Jehovah’s Witnesses who are often seen going door-to-door to share their erroneous doctrines (i.e., a created Christ, no hell and Trinity, etc). One doctrinal reason behind their assiduous evangelism is the belief that unless they work hard, those who are not part of the 144,000 “Congregation of God” will not survive the Battle of Armageddon (Rev. 16:16). So, if Paul were talking about the importance of evangelism to the Corinthians, he might have said, “Now if there is no hope of surviving the Battle of Armageddon, what will those Jehovah’s Witnesses, who assiduously evangelize door-to-door, do? If they are not spared from the final battle at all, why are they evangelizing so hard?” By saying this, Paul would be stressing the importance of evangelizing but not for the erroneous reason of surviving the Armageddon. In the same way, Paul is for baptism and belief in the resurrection, but not for the erroneous reason that those who died without believing in Christ could enter heaven on account a vicarious baptism. Among other NT passages, the Mormons should take seriously Heb. 9:27 (ESV): “And just as it is appointed for man to die once, and after that comes judgment.”
Second view: It could be that the believing relatives of Christians, who died before getting baptized, underwent baptism on their behalf. The fact is, baptism was a big deal in the early church whose doctrinal worth was sometimes boosted by not-so-healthy theology (e.g., no forgiveness after baptism, baptismal regeneration, etc.). Perhaps, in that context, these well-meaning family members overextended themselves by making sure that their believing relatives who died without being baptized would spiritually benefit by their vicarious act—even if, in reality, it made no difference.
Water baptism is a rite that represents our identification with what has already been done spiritually: Christ died for our sins and then rose from the dead to conquer death and to impart eternal life. When a person believes this, he is saved, whether he is baptized or not.
 The Mormons teach that while belief in Christ removes the original sin, it is right conduct (a set of thousand of rules) that will get them into the Celestial Heaven—the highest among the three Mormon heavens.