In Greek culture, the matter is bad and the spirit is good, i.e., a person is released from the matter when he dies. It was difficult for them to understand that the Lord's creation is good. For them, Lord's creation was some kind of prison and we are set free only when dying. So, how come "we resurrect from the death"?
Jesus took the price for our sins and Jesus resurrected from the death, but it was difficult to them understand why Jesus would resurrect to this world made of matter? How come Jesus had a body?
Paul argued that there were many alive witness that they could inquire, but for me, the most intriguing was James, Jesus's brother.
Before resurrection, James and his brothers didn't believe in Jesus as the Messiah but Paul wrote:
7 then He appeared to James, then to all the apostles; 8 and last of all, as to one untimely born, He appeared to me also.
James became the leader in Jerusalem. The epistle of James begins with:
"James, a bond-servant of God and of the Lord Jesus Christ,"
What made James declare that he is a bond-servant of his brother Jesus? The resurrection.
Paul stated that it is crucial that the Corinthians believe in resurrection:
17 and if Christ has not been raised, your faith is worthless; you are still in your sins.
To be a Christian is to believe in Jesus and his sacrifice for our sins, but it is also to believe in resurrection.
I am getting old. I was born with a problem in my heart valve that is now being calcified, i.e. it is loosing the capacity to correctly bomb my blood. I am retired and I really wanted to enjoy my retirement as long as possible; so this discovery about this valve problem was a very bad news to me. However, for me as a Christian it doesn't lead me into despair because I believe in the resurrection.