For those who are curious as how Seventh Day Adventists interpret 1 Cor 15:29 and baptism for the dead, the following is from a SDA apologist. SDA theology is also informed by "souls sleep." On this doctrinal error, see Response to Douglas V. Pond on Biblical and LDS Anthropology and Eschatology
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?
This is perhaps one of the most puzzling things that Paul wrote in his epistles. One explanation that fits in perfectly with Paul’s line
of reasoning revolves around the meaning of the word “for.” The Greek word is “huper,”
and the general translation is “in behalf of.” But there are exceptions to this
meaning. Sometimes the word is used in the sense of “considering” or “in view
of.”
For example, 2 Thessalonians 1:4 says: “So that we
ourselves glory in you in the churches of God for your patience and faith in
all your persecutions . . .” Here Paul is saying, “We glory in you considering
(or in view of) your patience and faith.” In Romans 15:9—which reads, “And that
the Gentiles might glorify God for his mercy . . .” –it can be translated “considering
his mercy.”
Please notice now that this same word “huper,” which is
translated “for,” is used both ways in 1 Corinthians 15:29: “Else what they
shall do which are baptized for (considering) the dead, if the dead rise not at
all? why are they then baptized for (in view of) the dead?”
If we substitute this other meaning of the word “for,”
the text makes perfect sense. Paul’s whole theme in the chapter if the
resurrection—its importance and necessity. He is saying, “Why even be baptized
if there is no resurrection from the dead?” The very meaning of baptism would
be nullified. With no resurrection, the entire symbolism of baptism—death, burial,
and resurrection—would be reduced to an empty ritual. (Joe Crews, Answers to
Difficult Bible Texts [Roseville, Calif.: Amazing Facts International,
1988. 2013], 60-61)