1 Corinthians 15:20

But now is Christ risen from the dead, and become the firstfruits of them that slept (KJV)

Then: Finished listing the consequences of no resurrection, Paul wants the Corinthians remember Christ, the first fruit of those who were raised. Crops grow every season and the early fruit, the one that seems to take forever to ripen, is the most enjoyed when picked and eaten. Since the creation story, people waited for the Lord to send the promised one, and when he did, he was crucified and resurrected. That resurrection was the first of many more to come. The Corinthians can take heart that all they just heard prepared them to address others. Now they could evaluate their own perceptions, solidify their own thoughts and use their conclusions when they in turn help others to leave lives characterized by disbelief in Christ. The Corinthians are now reassured that God's plan lives on.

Now: We sense that this passage, verses 20-28, is a product of Paul's time spent reorienting everything he knew about theology before his visit from Christ. He had to understand it himself. That's why it is easier for us to understand - he used what he knew and gave it to all generations.