1 Corinthians 15:12

Now if Christ be preached that he rose from the dead, how say some among you that there is no resurrection of the dead? (KJV)

Then: Many had problems with the idea of a resurrection. Paul's first point is that since resurrection is clearly possible, Christ rose from the dead, then no one can say that it just can't happen. After all more than 500 witnesses saw and talked to him. It can happen because it did happen. Paul as a Pharisee no longer has to look for arcane or obscure defenses for his former belief. The evidence exists in the risen Lord (Harn, p. 219).

Now: Believers know the story of the death, burial and resurrection. From the time they first believe, they have an internal resolution that the Holy Spirit has confirmed their knowledge of the "I am." God is, and through his son, they have salvation. Therefore, a belief in resurrection is not an issue. Sometimes, for purposes of comparison, the metaphorsis of caterpillars to butterflies or seeds to plants is presented, but isn't really necessary for those who pray and speak daily with the God of heaven. The Lord who made it possible for physical creations to change form has no difficulty in changing physical bodies into spiritual ones. His power and authority transcend and encompass both worlds.

Extra Source: The Lectionary Commentary: Theological Exegesis for Sunday's Texts ed. by Roger E. Van Harn (Grand Rapids MI: Wm B. Eerdman's Pub. Co., 2005) http://books.google.com/books?id=afCD6cgnAN8C&pg=PR9&lpg=PR9&dq=1+corinthians+15+commentary&source=bl&ots=ZynkCVlguV&sig=XYIf7ZwUxR6y7P9zNz_YNUOnzhc&hl=en&ei=ljsES6acEdXVlAeendnuAQ&sa=X&oi=book_result&ct=result&resnum=10&ved=0CCYQ6AEwCTge#v=onepage&q=&f=false