Against Heresies by Irenaeus (2nd cent - c. 202 CE)

St. Irenaeus, Bishop of Lyons, describes several schools of Gnosticism which were prevalent among pre-Nicene Christianity. He then refutes these beliefs as heresies by contrasting them with what he describes as catholic, orthodox Christianity. Against Heresies demonstrates that earliest Christianity was a fascinating and diverse plethora of beliefs, debates, and schisms. (Summary by JoeD)