Easter Sunday represents the foundational claim of Christian faith, the highest day of the Christian year as celebration of Jesus' resurrection. But many Christians are unsure what the claim that Jesus had been raised to new life after being crucified actually means—while non-Christians often find the whole idea of resurrection bemusing and even ridiculous.
These differences over what Jesus' resurrection represents and discomfort with the whole idea are nothing new, however: Christians in the first few centuries also had difficulty embracing the idea of a real, bodily resurrection. Then, as now, resurrection was not the favored post-death existence—people much preferred to think that after dying, souls headed to some ethereal realm of light and tranquillity. During the Roman period, many regarded the body as a pitiful thing at best and at worst a real drag upon the soul, even a kind of prison from which the soul was liberated at death. So, it's not surprising that there were Christians who simply found bodily resurrection stupid and repugnant. To make the idea palatable, they instead interpreted all references to Jesus' resurrection in strictly spiritual terms. Some thought of Jesus as having shed his earthly body in his death, assuming a purely spiritual state, and returning to his original status in the divine realm. In other cases, Jesus' earthly body and his death were even seen as illusory, the divine Christ merely appearing to have a normal body (rather like Clark Kent!).
The idea of a real, personal resurrection—meaning a new bodily existence of individuals after death, in one way or another—did not originate with Christianity or with claims about Jesus. Instead, it seems to be first clearly reflected in Jewish texts dated to sometime in the second century B.C., such as the biblical book of Daniel 12:2. At the time, it was a genuinely innovative idea. (Alan Segal's book Life After Death gives an expansive discussion of the origins of the idea of resurrection.) Many peoples of the ancient world hoped for one or another sort of eternal life, but it was usually thought of as a kind of bodiless existence of soul or spirit set in realms of the dead that might or might not be happy, pleasant places. In still other expectations, death might bring a merging of individuals with some ocean of being, like a drop of water falling into the sea.
The ancient Jewish and early Christian idea of personal resurrection represented a new emphasis on individuals and the importance of embodied existence beyond the mere survival or enhancement of the soul, although there was debate about the precise nature of the post-resurrection body. Some seem to have supposed it would be a new body of flesh and bones, closely linked to the corpse in the grave but not liable to decay or death. Others imagined a body more like that of an angel. But whatever its precise nature, the hope of resurrection reflected a strongly holistic view of the person as requiring some sort of body to be complete. With ancient Jews, early Christians saw resurrection as an act of God, a divine gift of radically new life, not an expression of some inherent immortality of the soul. That is, the dead don't rise by themselves; they are raised by God and will experience resurrection collectively as one of the events that comprise God's future redemption of the world and vindication of the righteous.
In the ancient Judaism of Jesus' time, however, resurrection was not universally affirmed. Some devout Jews (particularly the religious party called Sadducees) apparently considered the whole idea ridiculous, as evidenced by the New Testament, which gives us some of the most direct references to disputes among ancient Jews about the matter. In Mark 12:18-27, Sadducees taunt Jesus with a question about a woman married several times, asking him whose wife she will be following the resurrection. Jesus strongly affirms resurrection, but he insists that those resurrected will not marry and portrays the Sadducees' question as reflecting a foolish ignorance of God's power.
In the earliest expressions of their faith that we have, Christians claimed that Jesus' resurrection showed that God singled out Jesus ahead of the future resurrection of the dead to show him uniquely worthy to be lord of all the elect. However, the paradigmatic significance of Jesus' resurrection was also very important for early Christians.