Generally dualists with elaborate mythologies and cosmologies.
Believed they possessed "gnosis" (secret knowledge) for salvation.
Rejected Jesus's humanity and believed the human body/physical world was evil, created by an "evil God."
Divine sparks (true spirits) were imprisoned in physical bodies, and Jesus's mission was to liberate them.
Valentinus: A prominent 2nd-century Gnostic leader from Egypt, possibly a disciple of Paul's disciple.
His teachings were condemned by proto-Orthodox leaders like Tertullian and Irenaeus.
The "Gospel of Truth" from the Nag Hammadi library may be his work.
Unlike other groups, Gnostics often existed as secret groups within other Christian churches (especially proto-Orthodox ones), making them harder to root out.
Possible warnings against Gnostics appear in Second Timothy, criticizing their spiritualized resurrection teachings.