Docetae Docetism, which in the latter half of the second century took form in the sect of the Valentinians — so named after Valentinus — is, in fact, only a form of Gnosticism — a form, moreover, which played a most important part in the general movement of Gnosticism. Its prominent teachers, as Valentinus — a man of great depth, ingenuity, and power of imagination Cassianus, and Bardesanes, are reckoned among the Gnostics. How Docetism is to be distinguished from general Gnosticism is not easy to be stated in a brief article; the Church histories must be consulted on this point. The dualism of the Oriental philosophy, the elements of which were extensively embraced in all forms of Gnosticism, especially the view which held to the inherent evil of matter, rendered it impossible for the Gnostics to come to any right view of the union of the divine and human in Christ's person. In order to remove the author of all good from all contact with matter, which they conceived to be the same as evil, they called in the aid of Oriental philosophy in order to people the space between God and matter with a vast succession of superhuman beings as mediators between God and the world. These, emanating from the Deity, were called aeons; among these the highest rank was assigned to Christ. Here, however, they seem to have split. "Many imagined that Jesus was a mere man, and maintained that the aeon Christ descended upon the man Jesus at his baptism, and left him immediately before his crucifixion, so that Christ was not, in fact, subjected to pain and death; while others held that the body, with which Christ appeared to be invested, was not really human and passable, but unsubstantial or etherial, or, at least, immaterial: these last were called Docetae" (Waddington's Hist. of the Church, pages 74, 75). They denied the whole humanity of Christ, regarding it only as a deceptive show, a mere vision. This the sense of the Church could not bear. "They who would make nothing but a spectre are themselves spectres — spectral men," is an expression ascribed to Ignatius. Tertullian says to the Docetae, "How is it that you make the half of Christ a lie? He was all truth." And again, "You are offended when the child is nourished and fondled in its swaddling-clothes. This reverence shown to nature you despise; and how were you born yourself? Christ, at least, loved man in this condition. For his sake he came down from above; for his sake he submitted to every sort of degradation-to death itself. In loving man he loved even his birth, even his flesh" (Neander, Church Hist. 2:369). Neander says: "One consequence of the disruption of the divine and the human by Gnosticism was Docetism, which altogether denied the real, humanly-sensuous side of Christ's life, and only acknowledged as real the revelation of the divine Being. Preparation for this view had been made among the Jewish theologians by the representation that it was one of the privileges of a superior spirit to appear in a variety of forms. Philo's explanation of the Angelophanies, and the Christology of the Clementine homilies, furnish evidence of this. According to that Docetic conception, the heavenly Being, whose nature is pure light, suddenly came forth as a sensuous apparition. All sensuousness is only an illusion practiced by the divine Genius. Hence the latter by no means attached himself to the Demiurgos; only an appearance of him descended into this world" (Neander, Hist. of Dogmas, 1:194).
Docetism was a most subtle element, which wrought variously before it had any discernible concentration in any leading men or sects, and it infused its unreal and fantastic leaven into various Gnostic sects, and other later ones which grew out of Gnosticism. It was a deep, natural, rationalistic, pseudo-spiritualistic, anti-incarnation element. It was firmly set against the real union of the divine and human in Christ, and against all dogmas which depend upon the reality of the incarnation. Hagenbach says: "The Docete, whom Ignatius (ad Eph. 7, 8, ad Smyrn., c. 1-8) already opposed, and probably even the apostle John (1Jo 1:1-3; 1Jo 4:2 sq.; 2 John, 7) (on the question whether he alludes to them in his prologue to his gospel, see Licke, in loc.) may be considered as the forerunners of the Gnostics (Burton, Bampton Lect. page 158 sq.). They form the most decided contrast with the Ebionites, inasmuch as they not only maintain (in opposition to them) the divinity of Christ, but also merge his human nature, to which the Ebionites exclusively confined themselves, in a mere phantom (by denying that he possessed a real body). Ebionitism (Nazaritism) and Docetism form, according to Schleiermacher (Glaubenslehre, 1:124), natural heresies, and complete each other, as far as this can be the case with one-sided opinions; but they quite as easily pass over from the one to the other (comp. Dorner, Geschichte der Christologie, page 349 sq.)" (Hagenbach, Hist. of Doctrines, 1:48). The fathers were compelled to war with this subtle Docetism constantly, as it ever broke out in new places, and attacked the true Christian faith at most unexpected points. Even some of them, as Clement and Hilary, were temporarily ensnared by some of its subtleties. Docetism (the speculative view of Christ's person) reappears in modern times in the mythical and spiritualistic theories which "attempt to reduce Christianity to an aesthetic religion, in which no realities are necessary but such as the human mind can supply as ideas" (Martensen, Dognmatics, § 128). See Schaff, Hist. of the Christian Church, 1, § 71; Neander, Church History (Torrey's edit.), 1:386; 2:717; Hase, Church History, § 37; Hagenbach, History of Doctrines; Dorner, Doctrine of the Person of Christ (Edinb. transl.), div. 1, volume 1.