Among the many issues troubling the church in Corinth is apparently doubt among some of the saints there about resurrection of the body.  Some apparently have doubts about whether it actually happens, and actually happened for Christ. Others want to know what kind of body is raised: a physical one or a spiritual one, or something else.  Paul writes to reassure them, and to scold them. ("Fool!" he exclaims in verse 36).

Paul's reasoning in chapter 15 has long been inspiring for me, but more than that, it defines for all of us, I think, a core tenet of our faith.  If there is no resurrection, then Christ has not been raised, and our faith and our proclamation are worthless. If Christ has not been raised, then we are wasting our time at playing church, and we should find more worthwhile activities to occupy our time, our effort, our money, our emotional toil.  (None of these things are actually "ours" according to Christian teaching: they are God's, and we are stewards of them.)

If Christ has not been raised, then we will not be raised either. Our faith is then futile, and we are still drowning in our sin (vs. 17).  If it is for this life only that we have hoped in Christ, then we are, of all people, the most to be pitied. (vs. 19)
 
Verse 20: "But in fact, Christ has been raised from the dead."Our faith is built upon joyful and firm affirmation of that statement, even though our faith will of a certainty be shaken from time to time.  Or more often than that.  Even so, we affirm with saints from all times and places that, yes indeed, "Christ has been raised."