What does 1 Corinthians 12:18 mean?

Here, Scripture extends the illustration of the church as the body of Christ. Paul has imagined parts of the body trying to quit because they cannot be some different member with a different function. Apparently, though, that's exactly what was happening in Corinth. Perhaps some Christians wanted to stop belonging to the church, at all, because they did not like the role they were given by the Spirit to serve in the church.

Now Paul drives home the point that body parts don't choose their jobs. God does that. He placed each body part in the best place on the body to do its work, giving each part the exact job for which it was designed. Those parts are meant to work in harmony—when certain parts refuse to work, the body cannot function as it was intended.

Paul's point is that God does the same with the church. Paul wrote in verse 11 that the Spirit matches every believer with their personal gift or gifts, to be used to serve the other members in the church and the body of Christ as a whole. God chooses our role; we don't decide what part in the church we would like to play. As Paul describes it, we receive the role and fill the part we're given.