What Is the Repugnant Conclusion?

The philosopher Derek Parfett identified a problem with the asymmetry argument. He thought it meant we had to embrace a conclusion which he regarded as repugnant. However, there are many views that say that as long as a life is sufficiently good, then it's a good thing to bring that life into existence. But it has to be sufficiently good - if it's merely a little bit above zero, that's not a good thing.