A Docetist argues that Christ Jesus only seemed to be (Gk. δοκέω – dokeō) human. He appeared to be a Jewish man but he did not possess a true corporal earthly body. Swayed by Gnosticism, that assumes the material creation is innately evil, it is foolish and shameful, according to a gnostic docetist, to think that Logos, who was in form of God, would take upon Himself an unworthy form of a creature.
Millard J. Erickson explained:
Docetism is in essence a Christology heavily influenced by basic Greek assumptions of both the Platonic and Aristotelian varieties. Plato taught the idea of gradations of reality. Spirit or mind or thought is the highest. Matter or the material is less real. With this distinction of ontological gradations of reality, there came to be ethical gradations as well. Thus, matter came to be thought of as morally bad. (Erickson 1998: 729)
Norman Geisler quotes Bettenson’s explanation of docetism as “[t]he assertion that Christ’s human body was a phantasm, and that his suffering and death were mere appearances. ‘If he suffered he was not God; if he was God he did not suffer’” (Geisler 1999: 202)
Ekkehard Mühlenberg informs that the earliest reference to the concept of docetism is found in the letters of Ignatius of Antioch (d. ca. 107) to the churches of Asia Minor. He explained that these epistles Ignatius warned the churches “to beware of false teachers who maintain that Jesus Christ “only appeared to suffer” and thus to undergo birth, eating and drinking, persecution and crucifixion under Pontius Pilate, and resurrection in appearance only.” (Mühlenberg 2003: 862).
In Elucidations, Clement of Alexandria explicated that the doctrine of Christ Jesus only appeared human, namely “docetism of Cassian, who had presumed to speak of the body of Jesus as a phantasm” (Robert Ed 1885: 407), is destructive to the Christ of the Gospel.
North African Carthaginian, Tertullian(c. 160 – c. 225) joined forces in condemning Gnostic docetism. In his works against the teachings of Marcion, he pointed out “[i]f you[Marcion] allege that the Creator practised deception in any instance, there was a far greater mendacity in your Christ, whose very body was unreal.” (ibid 320) Refuting Marcion’s docetism, Tertullian contended:
But when he adds, that “he bare in his body the scars of Christ”—since scars, of course, are accidents of body—he therefore expressed the truth, that the flesh of Christ is not putative, but real and substantial, the scars of which he represents as borne upon his body. (ibid 438)
Tertullian explained to Marcion that there are other quite equally foolish things as Christ Jesus taking upon flesh. “Humiliations and sufferings of God”, “Crucified God” for example. He went on:
For which is more unworthy of God, which is more likely to raise a blush of shame, that God should be born, or that He should die? that He should bear the flesh, or the cross? be circumcised, or be crucified? be cradled, or be coffined? be laid in a manger, or in a tomb?
If Marcion’s Jesus only appeared human, Tertullian argued, then Marcion had “cut away all sufferings from Christ, on the ground that, as a mere phantom, He was incapable of experiencing them?” (ibid 525)
Tertullian also showed that “[Christ Jesus] hungered under the devil’s temptation; He thirsted with the woman of Samaria; He wept over Lazarus; He trembles at death (for “the flesh,” as He says, “is weak”); at last, He pours out His blood.” (ibid, 530) These were “celestial marks” that showed Christ as not only appear human but was really human.
Countering Docetism, Justin Martyr emphasized that Christ Jesus was fully human thus experience really pain. Explaining Christ Jesus at Gethsemane to Trypho, Justin contended:
‘If it be possible, let this cup pass:’ His heart and also His bones trembling; His heart being like wax melting in His belly in order that we may perceive that the Father wished His Son really to undergo such sufferings for our sakes, and may not say that He, being the Son of God, did not feel what was happening to Him and inflicted on Him. (ibid 251)
New Testament writers also contended against docetism. The author of first and second Epistles of John, warned that “many deceivers have gone out into the world, those who do not confess the coming of Jesus Christ in the flesh” (2 John 7a) and “every spirit that confesses that Jesus Christ has come in the flesh is from God, and every spirit that does not confess Jesus is not from God.” (1 John 4:2-3b)
A nail in docetism doctrine coffin is found in Hebrews 2:17. The Son of God partook of the blood and flesh because “he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people.”
Contra Arianism, Docetism strongly affirmed the Deity of Christ, but at the cost of denying His humanity.
Question: Some theologians have accused the Gospel of John’s Christology as a road to docetism. Is there truth in their accusation? Give reasons
 Justin Martyr: Dialogue with Trypho Chapter 103
Erickson, M. J. (1998). Christian theology (2nd ed.). Grand Rapids, Mich.: Baker Book House.
Geisler, N. L. (1999). Baker encyclopedia of Christian apologetics. Baker reference library. Grand Rapids, Mich.: Baker Books.
Mühlenberg, Ekkehard (2003) “Docetism” in Fahlbusch, E., & Bromiley, G. W. (1999-2003). Vol. 1: The encyclopedia of Christianity. Grand Rapids, Mich.; Leiden, Netherlands: Wm. B. Eerdmans; Brill.
Roberts, J. Donaldson & A. C. Coxe, Ed (1885): The Ante-Nicene Fathers, Volume II: Fathers of the Second Century: Hermas, Tatian, Athenagoras, Theophilus, and Clement of Alexandria (Entire). (A..). Buffalo, NY: Christian Literature Company.