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?

Then: For Paul and the Corinthians both, the main point of the verse is the absurdity of the act of baptism if there is no resurrection. Without it, what happens to all those who were baptized? Nothing. The Corinthians understood the logic. They also understood what Paul meant by the phrase "baptized for the dead."

Now: Today's Christians understand only the context, but not the phrase or practice of "baptized for the dead." N. T. Wright profers two common understandings (1) a practice of some being baptized for those believers who died (martydom?) before they personally could be baptized or (2) when some Christians were baptized after the loss of a beloved Christian friend. They wanted the hope of reunion. Paul might also mean that anyone who does not believe in Christ is dead - spiritually dead. So he/she takes on the task of being baptized for his/her own dead body. The arguments and ideas are complex and many. A comprehensive review is in the October--November 1995 issue of Biblioteca Sacra. Anyone can read it and be confused too.

Extra Source: "Another Look at 1 Corinthians 15:29, 'Baptized for the Dead'" by John D. Reaume, Bibliotheca Sacra 152 (October-December 1995) 457-75.