Against Heresies can be dated to sometime between 174 and 189 AD, as the list of the Bishops of Rome includes
Eleutherius, but not his successor
Victor. The earliest manuscript fragment of
Against Heresies,
P. Oxy. 405, dates to around 200
AD. Irenaeus' primary goal in writing
Against Heresies was to attack sects that deviated from Christianity, mainly the
Gnostics and
Marcionites. In particular, he sought to disprove what he saw as incorrect interpretations of scripture on the part of Gnostics such as
Valentinus. Irenaeus sought to present "what was understood as an authentic form of century-old Christian tradition against various forms of Gnosticism." As James VanderKam notes, elements of this early Christian tradition drawn upon by Irenaeus include apocalyptic traditions such as
1 Enoch. As bishop, Irenaeus felt compelled to keep a close eye on the Valentinians and to safeguard the church from them. In order to fulfill this duty, Irenaeus became well informed of Gnostic doctrines and traditions. His studies of Gnosticism eventually led to the compilation of this treatise. ==Main ideas==