Having explained the historical verifiability of the Resurrection in the first eleven verses of 1 Corinthians 15, St Paul then explains the theological necessity of the Resurrection in verse 12-19.
His entire premise is built upon the reality of resurrection itself. Paul stands in opposition to the pagan ideas of his day. His Gentile readers in the Corinthian church will have been brought up in a worldview that had no place for resurrection. You might have a consciousness after death, but your body was finished. Of course Paul doesn’t even go the way of some modern thinkers (and a lot of non-thinkers I’ve met) who presume that resurrection is simply an impossibility because it cannot be scientifically explained.
Paul was also in opposition to a minority among the Jews who were, or sided with, the Sadducees. Most Jews of the Second Temple period (which was about to end) believed in a bodily resurrection, but only at the end of time. Paul will deal with them in the next section of his argument.
Here he is saying that if resurrection is not the way God does things, then the whole story is pointless. The whole history of salvation from the Old Testament is pointless. Jesus’ death is pointless.
To have any Christian faith whatsoever, a person has to first believe in resurrection and then in the Resurrection. To claim to be a Christian and yet believe in some sort of non-physical “spiritual” resurrection, in which Jesus comes alive in the hearts of His otherwise disappointed disciples is for Paul completely nonsensical.
Then Paul makes a claim that runs up against much of our Western cruciform preaching and singing. The cross was not sufficient to save us. If this statement shocks you and you don’t have 1 Corinthians 15 to hand, let me refresh your memory of verses 17 and 18: And if Christ is not risen, your faith is futile; you are still in your sins! Then also those who have fallen asleep in Christ have perished.
Good Friday without Easter Sunday is just a dead itinerant preacher nailed to two pieces of lumber. You can believe that Jesus died for your sins with all your heart and it won’t matter unless the tomb is empty.
In Romans, Paul writes extensively about the importance of the death of Christ. However, when he makes a brief summary of the requirement for salvation for both the Jew and the Gentile, in the oft quoted 10:9, that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved.
The Resurrection presumes the Crucifixion. One cannot rise unless one is, in fact, dead. The Crucifixion requires the Resurrection. Without the power of the Resurrection, there is no power in the cross. There is no power over sin and death. There is no King and no kingdom, no future and no hope.