Cassianus was the founder. Docetism, however, undoubtedly
existed before the time of Cassianus. The origin of the heresy is to be
sought in the Greek, Alexandrine and Oriental philosophizing about the
imperfection or rather the essential impurity of matter. Traces of a
Jewish Docetism are to be found in Philo; and in the Christian form it
is generally supposed to be combated in the writings of John,[2] and
more formally in the epistles of Ignatius.[3] It differed much in its
complexion according to the points of view adopted by the different
authors. Among the Gnostics and Manichaeans it existed in its most
developed type, and in a milder form it is to be found even in the
writings of the orthodox teachers. The more thoroughgoing Docetae
assumed the position that Christ was born without any participation of
matter; and that all the acts and sufferings of his human life,
including the crucifixion, were only apparent. They denied accordingly,
the resurrection and the ascent into heaven. To this class belonged
Dositheus, Saturninus, Cerdo, Marcion and their followers, the Ophites,
Manichaeans and others. Marcion, for example, regarded the body of
Christ merely as an "umbra," a "phantasma." His denial (due to his
abhorrence of the world) that Jesus was born or subjected to human
development, is in striking contrast to the value which he sets on
Christ's death on the cross. The other, or milder school of Docetae,
attributed to Christ an ethereal and heavenly instead of a truly human
body. Amongst these were Valentinus, Bardesanes, Basilides, Tatian and
their followers. They varied considerably in their estimation of the
share which this body had in the real actions and sufferings of Christ.
Clement and Origen, at the head of the Alexandrian school, took a
somewhat subtle view of the Incarnation, and Docetism pervades their
controversies with the Monarchians. Hilary especially illustrates the
prevalence of naive Docetic views as regards the details of the
Incarnation. Docetic tendencies have also been developed in later
periods of ecclesiastical history, as for example by the Priscillianists
and the Bogomils, and also since the Reformation by Jacob Boehme, Menno
Simons and a small fraction of the Anabaptists. Docetism springs from
the same roots as Gnosticism, and the Gnostics generally held Docetic
views (see GNOSTICISM).

FOOTNOTES:

[1] Not a distinct sect, but a continuous type of Christology.
Hippolytus, howev