Docetism is not properly a Christian heresy at all, as it did not arise in the Church from the misundertanding of a dogma by the faithful, but rather came from without. Gnostics starting from the principle of antagonism between matter and spirit, and making all salvation consist in becoming free from the bondage of matter and returning as pure spirit to the Supreme Spirit, could not possibly accept the sentence, "the Word was made flesh", in a literal sense. In order to borrow from Christianity the doctrine of a Saviour who was Son of the Good God, they were forced to modify the doctrine of the Incarnation. Their embarrassment with this dogma caused many vacinations and inconsistencies; some holding the indwelling of an Aeon in a body which was indeed real body or humanity at all; others denying the actual objective existence of any body or humanity at all; others allowing a "psychic", but not a "hylic" or really material body; others believing in a real, yet not human "sidereal" body; others again accepting the of the body but not the reality of the birth from a woman, or the reality of the passion and death on the cross. Christ only seemed to suffer, either because He ingeniously and miraculously substituted someone else to bear the pain, or because the occurence on Calvary was a visual deception. Simon Magus first spoke of a "putative passion of Christ and blasphemously asserted that it was really he, Simon himself, who underwent these apparent sufferings. "As the angels governed this world badly because each angel coveted the principality for himself he Simon came to improve matters, and was transfigured and rendered like unto the Virtues and Powers and Angels, so that he appeared amongst men as man though he was no man and was believed to have suffered in Judea though he had not suffered" (passum in Judea putatum cum non esset passus -- Irenaeus, Adv. Haer. I, xxiii sqq.). The mention of the demiurgic angels stamps this passage as a piece of Gnosticism. Soon after a Syrian Gnostic of Antioch, Saturninus or Saturnilus (about 125) made Christ the chief of the Aeons, but tried to show that the Savior was unborn (agenneton) and without body (asomaton) and without form (aneideon) and only apparently (phantasia) seen as man (Irenaeus, Adv. Haer., XXIV, ii).
Another Syrian Gnostic, Cerdo, who came to Rome under Pope Hyginus (137) and became the master of Marcion, taught that "Christ, the Son of the Highest God, appeared without birth from the Virgin, yea without any birth on earth as man". All this is natural enough, for matter not being the creation of the Highest God but of the Demiurge, Christ could have none of it. This is clearly brought out by Tertullian in his polemic against Marcion. According to this heresiarch (140) Christ, without passing through the womb of Mary and endowed with only a putative body, suddenly came from heaven to Capharnaum in the fifteenth year of Tiberius; and Tertullian remarks: "All these tricks about a putative corporeality Marcion has adopted lest the truth of Christ's birth should be argued from the reality of his human nature, and thus Christ should be vindicated as the work of the Creator Demiurge and be shown to have human flesh even as he had human birth" (Adv. Marc., III, xi). Tertullian further states that Marcion's chief disciple, Apelles, sightly modified his master's system, accepting indeed the truth of Christ's flesh, but strenously denying the truth of His birth. He contended that Christ had an astral body made of superior substance, and he compared the Incarnation to the appearance of the angel to Abraham. This, Tertullian sarcastically remarks, is getting from the frying pan into fire, de calcariâ in carbonariam. Valentinus the Egyptian attempted to accommodate his system still more closely to Christian doctrine by admitting not merely the reality of the Saviour's body but even a seeming birth, saying that the Saviour's body passed through Mary as through a channel (hos dia solenos) though he took nothing from her, but had a body from above. This approximation to orthodoxy, however, was only apparent, for Valentinus distinguished between Christ and Jesus. Christ and the Holy Ghost were emanations from the Aeons together proceeded Jesus the Saviour, who became united with the Messias of the Demiurge.
In the East, Marinus and the school of Bardesanes, though not Bardesanes himself, held similar views with regard to Christ's astral body and seeming birth. In the West, Ptolemy reduced Docetism to a minimum by saying that Christ was indeed a real man, but His substance was a compound of the pneumatic and the psychic (spiritual and ethereal). The pneumatic He received from Achamoth or Wisdom, the psychic from the Demiurge, His psychic nature enabled him to suffer and feel pain, though He possessed nothing grossly material. (Irenaeus, Adv. Haer., I, xii, II, iv). As the Docetae objected to the reality of the birth, so from the first they particularly objected to the reality of the passion. Hence the clumsy attempts at substitution of another victim by Basilides and others. According to Basilides, Christ seemed to men to be a man and to have performed miracles. It was not, however, Christ, who suffered but Simon of Cyrenes who was constrained to carry the cross and was mistakenly crucified in Christ's stead. Simon having received Jesus' form, Jesus returned Simon's and thus stood by and laughed. Simon was crucified and Jesus returned to his father (Irenaeus, Adv. Char., 1, xxiv). According to some apocrypha it was Judas, not Simon the Cyrenean, who was thus substituted. Hippolytus describes a Gnostic sect who took the name of Docetae, though for what reason is not apparent, especially as their semblance theory was the least pronounced feature in their system. Their views were in close affinity to those of the Valentians. The primal Being is, so to speak, the seed of a fig-tree, small in size but infinite in power; from it proceed three Aeons, tree, leaves, fruit, which, multiplied with the perfect number ten, become thirty. These thirty Aeons together fructify one of themselves, from whom proceeds the Virgin-Saviour, a perfect representation of the Highest God. The Saviour's task is to hinder further transference of souls from body to body, which is the work of the Great Archon, the Creator of the world. The Saviour enters the world unnoticed, unknown, obscure. An angel announced the glad tidings to Mary. He was born and did all the things that are written of him in the Gospels. But in baptism he received the figure and seal of another body besides that born of the Virgin. The object of this was that when the Archon condemned his own peculiar figment of flesh to the death of the cross, the soul of Jesus--that soul which had been nourished in the body born of the Virgin--might strip off that body and nail it to the accursed tree. In the pneumatic body received at baptism Jesus could triumph over the Archon, whose evil intent he had eluded.
The earlier Docetism seemed destined to die with the death of Gnosticism, when it received a long lease of life as parasitic error to another heresy, that of Manichaeism. Manichaean Gnostics started with a two-fold eternal principle, good (spirit) and evil (matter). In order to add Christian soteriology to Iranian dualism, they were forced, as the Gnostics were, to tamper with the truth of the Incarnation. Manichees distinguished between a Jesus patibilis and a Jesus impatibilis or Christ. The latter was the light as dwelling in, or symbolized by, or personified under, the name of the Sun; the former was the light as imprisoned in matter and darkness; of which light each human soul was a spark. Jesus patibilis was therefore but a sign of the speech, an abstraction of the Good, the pure light above. In the reign of Tiberius Christ appears in Judea, Son of the Eternal Light and also Son of Man; but in the latter expression "man" is a technical Manichaean term for the Logos or World-Soul; both anthropos and pneuma are emanations of the Deity. Though Christ is son of man He has only a seeming body, and only seemingly suffers, His passion being called mystical fiction of the cross. It is obvious that this doctrine borrowed from that of the Incarnation nothing but a few names. Scattered instances of Docetism are found as far West as Spain among the Priscillianists of the fourth and the fifth century. The Paulicians in Armenia and the Selicians in Constantinople fostered these errors. The Paulicians existed even in the tenth century, denying the reality of Christ's birth and appealing to Luke, vii, 20. God, according to them, sent an angel to undergo the passion. Hence they worshipped not the cross but the Gospel, Christ's word. Among the Slavs the Bogomilae renewed the ancient fancy that Jesus entered Mary's body by the right ear, and received from her but an apparent body. In the West a council of Orléans in 1022 condemned thirteen Catharist heretics for denying the reality of Christ's life and death. In modern theosophic and spiritist circles this early heresy is being renewed by ideas scarcely less fanstastic than the wildest vagaries of old.