Yeah this is a pretty controversial passage. My view on this passage is a bit eccentric, but hopefully easy enough to communicate - here goes... first, the background:
1) The context of the letter
- Remember from ch1 (& ch10): The Corinthians are boasting about which apostle baptised them
- Remember from chs1-4: For Paul, the apostolic life is basically a life of death - because it imitates the cross
- The rest of 1 Corinthians can be read as Paul's charge to the cruciphobic Corinthians to "imitate him" as he imitates the cross
2) The context of the chapter
- The Corinthians are effectively denying the need for future resurrection
3) The function of the section (vv29-32)
- Paul is drawing attention to the fact that both Paul and the Corinthians themselves ACT as though there will be a resurrection of the dead
And now for my understanding of the verse:
"If there is no future resurrection of the dead, why do you Corinthians boast about being baptised in the name of metaphorically dead apostles?"
This reading of the verse may be supported by the fact that he goes on in v31: "I die every day"
In other words, there is no wacko practice of baptising people on behalf of actual corpses in view here: Paul is simply drawing attention to the ironic fact that the Corinthians are proudly boasting about baptism "on behalf of" Paul or Apollos, when those very apostles are the living dead. So if there is no future resurrection of the dead, the Corinthians' own actions are meaningless.
Like I say, it's a bit of an eccentric view, but I like it!