This is another of those matters about which Paul and
the Corinthians surely understood one another but which we cannot hope to
fathom. The most obvious reading of the text would suggest that there are some
at Corinth (note that Paul does not address them directly, but writes about
them as an example) who are being baptized in behalf of dead persons, perhaps
as representatives of dear ones who either never had a chance to respond to the
gospel or who had died while being drawn to the faith. But the truth is that we
simply do not know. Most surprising is that Paul did not oppose the
practice, which seems to suppose either that grace is transferrable or that one
can be a surrogate believer for another. Instead, Paul uses it to expose
its folly if there is no resurrection of the dead. (J. Paul Sampley, “The First
Letter to the Corinthians,” in The New Interpreter’s Bible, 12 vols.
[Nashville: Abingdon Press, 2002], 10:982, emphasis in bold added)