This verse has the reputation of being considered one of the most difficult, confused and obscure verses throughout the Bible.
The translation literally is as follows: "If this were not true, what will those who are baptized for the dead do, if the dead do not rise again at all? Why then are they baptized for the dead?" (You have the option between the singular and the plural for "the dead").
Theologians suggest more than thirty explanations for the meaning of this verse. The more cautious recommend only giving an opinion as to what we believe it means, with humility, because other brethren may have different interpretations which are just as feasible.
It should first be established what the verse does not teach, although it might seem viable at first sight. It certainly does not refer to a baptism "in proxy" (practised by Mormons), by which a living person is baptized in the name of another person who died without being baptized, to enjoy some blessing or virtue acquired by baptism. It is fundamentally wrong to base a doctrine on a single verse out of its context, and that clearly contradicts all the biblical teaching about baptism.
As the Apostle Paul is referring to “are they baptized”, and not to “we” or “you”, there is the argument that those people who were being baptized would not be Christian but belonged to some other group, mentioned only as an example of belief in resurrection. It would not have been the custom of believers in Christ, otherwise Paul would have pointed this out in his letter, and censored it as he explicitly did for wrong practices in that church. This explanation may be feasible, but it seems very unlikely that Paul would look for an example of faith in resurrection among unbelievers.
The key to a correct interpretation of the verse is to understand correctly the meaning of baptism, who is or are the "dead" in this text, and what really is meant by “baptized for the dead”.
1. Baptism: is a declaration of faith, made as a public testimony by those who have converted to Christ, symbolizing the voluntary death of self by immersion into water (a burial, as Christ was buried after dying on the cross) and resurrection to a new life in Christ by rising from the water (like Christ rose again on the third day), as we read in Romans 6:2 to 6. Through baptism, the believer identifies himself with Christ. This reveals the incoherence of the baptism of infants, the lack of correct symbolism in the baptism by sprinkling, and the uselessness of the baptism in water for salvation of the soul, for receiving the Holy Spirit and for other benefits that are unduly attributed to baptism.
2. The dead: literally could refer to the risen Lord Jesus, or believers who are still in a state of physical death.
3 .Baptism "for" or "to the dead": the original Greek "hoi baptizomenoi huper toŻn nekroŻn", contains the words "“huper toŻn” of which “huper" has several meanings, the primary being "over", which can mean “above", “beyond”, “across”, or “for the sake of”, “instead”, “regarding” and so on. Furthermore, as "ton nekron" can be singular or plural, it is not surprising that there are many explanations given for this verse!
Throughout this chapter, the main theme is resurrection, and it would be surprising if this verse did not fit this theme perfectly. It would be even worse if it introduced a subject alien to all biblical teaching, such as baptizing oneself for the benefit of another person, whether alive or dead. If this were the case, no doubt the Holy Spirit would have provided some teaching on such a doctrine. But on the contrary, the verse makes reference to something that is known not only by the church of Corinth, but must also by all who know and practice the teachings of Scripture.
The verse begins with the word "otherwise", or "If that wasn't true", and then demonstrates how the reality of the resurrection is of paramount importance to the Christian. Many explanations given by theologians can thus be eliminated and we will confine ourselves to the three most likely to provide the correct interpretation:
1. When this letter was written to the Church of Corinth, Christians were being persecuted in various places, and in consequence many concealed their faith by not getting baptized. Members of the churches were persecuted and martyred, opening "gaps" on the list of its members and motivating those in hiding to come forward and be baptized, to take the place of the dead and also become subject to the high risk of martyrdom. They literally were baptized "in place of the dead". Without faith in the resurrection of the dead, this would be a very reckless attitude, if not suicidal.
2. All sinners “die" when converting, because spiritually they "die to themselves so as to live in Christ" (baptism in water is a symbol of this spiritual baptism) – e.g. Colossians 2:12 and Romans 6:2-11. The doctrine of baptism had already been established and was clearly accepted by the members of the church of Corinth to whom this letter was addressed (Chapter 1:13-17). If the physical resurrection exposed in previous verses wasn't true, the doctrine of baptism must also be rejected, because every believer is baptized "over” or “through” the “Dead”, the Lord Jesus. This second interpretation has universal application while the first is limited to some believers in a special situation in times of great persecution. In any case, the baptism in water would be of no significance if Christ had not risen from the dead, and therefore for the believer there would also be no physical resurrection besides the spiritual one. It sets forth how the reality of the physical resurrection of Christ is vital for the Gospel.
3. The simplest and most literal explanation is given by W E Vine: "In connection with the significance of baptism, the twenty-ninth verse of 1 Corinthians 15 has been usually understood to refer to a certain ceremony which took place on the occasion of the burial of a believer. In view, however, of the absence of any other intimation in Scripture regarding such a ceremony, and the absence of any historical evidence thereof in apostolic times, or those which immediately followed, another meaning must be sought. Bearing in mind that the original was written without punctuation marks, let the first question mark in the verse be placed after the word "baptized," and the verse gives a meaning at once consistent with the doctrine of Scripture. The reading will thus be: "Else what shall they do which are baptized? It is for (i.e., 'in the interests of') the dead, if the dead are not raised at all. Why then are they baptized for them?" The first question, "What shall they do ... ?' is a way of asking what is the use or value of being baptized. The insertion of the words "It is," to provide the answer, is consistent with the fact that the verb "to be" is frequently omitted in the original, as is shown by the italicized words in several places in this very chapter. If there is no resurrection of the dead, the ordinance, instead of setting forth the identification of believers with the risen Christ, has no meaning at all either for Him or for them; for all perish at death: see verse 18. Both His command and their witness in the ordinance are null and void. They testify to doctrines that have no significance. Their baptism is therefore in the interests of dead ones." Vine’s “The church and the churches”.