Funny ...Paul didn't condemn it though.
But he clearly makes a distinction between those he considers "us" (i.e. "The Church") and "them". Note that in a letter addressed to the Corinthians in the Second Person, St. Paul suddenly shifts to the Third Person:
"Otherwise, what will they
do who are baptized for the dead if the dead do not rise at all? Why then, are they
baptized for the dead?"
If he was talking about an Apostolic Tradition which he wanted to use to emphasise his point about what we
as Christians believe, wouldn't it make more sense for him to say:
"Otherwise, why do we
baptize for the dead? if the dead do not rise at all? Why then do we
baptize for the dead?"
St. John Chryssostom says he was referring to the Marcionite heresy, Epiphanius says he was referring to the followers ofÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€š another Gnostic, Cerinthus, either way, it is clear from the wording used by St. Paul that he is talking about an unOrthodox, heretical practice.