"While the apostles were still surviving, while Christ's blood was still fresh in Judea, the Lord's body was asserted to be but a phantasm." -Jerome
Docetism is the belief that Jesus Christ did not have a physical body; rather, that his body was an illusion, as was his crucifixion.
This belief is most commonly attributed to the Gnostics, who believed that matter was evil, and hence that God would not take on a material body. This sort of statement, however, is rooted in the idea that a divine spark is imprisoned within the material body and that the material body is in itself an obstacle that prevents man from seeing his divine origin. Humanity is in essence asleep. It could be further explained as this — the human body is temporary, and the spirit is eternal—therefore, to say that the body of Jesus was an illusion and that his crucifixion was as well, could be compared to the same way a Buddhist speaks about illusion: illusion is everything that is temporary, not everything that is not real. Even so, saying that the human body is temporary has a tendency to undercut the importance of the belief in resurrection of the dead and the goodness of created matter, and is in opposition to the orthodox view.