In Christianity, Docetism (from the Greek δοκέω [dokeō], "to seem") is the belief that Jesus' physical body was an illusion, as was his crucifixion; that is, Jesus only seemed to have a physical body and to physically die, but in reality he was incorporeal, a pure spirit, and hence could not physically die. This belief treats the sentence "the Word was made Flesh" (John 1:14) as merely figurative. Docetism has historically been regarded as heretical by most Christian theologians
Docetism can be further explained as the view that since the human body is temporary and the spirit is eternal, the body of Jesus must have been an illusion and, likewise, his crucifixion. 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 this orthodox view. Docetism was rejected by the ecumenical councils and mainstream Christianity, and largely died out during the first millennium A.D. Gnostic movements that survived past that time, such as Catharism, incorporated docetism into their beliefs, but such movements were destroyed by the Albigensian Crusade (1209-1229).
Ignatius of Antioch wrote very harshly against docetism in around the year 110 AD in his letter to the Smyrnaeans. In 7:1, he said, "They [the docetists] abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again. They who deny the gift of God are perishing in their disputes". Since one of the main beliefs of docetism was that the body of Jesus was an illusion, docetists could not accept that the bread and wine used in the Eucharist were the actual flesh and blood of Jesus. Other detailed criticisms were given by Irenaeus and Tertullian.