In recent decades our view of Gnosticism has been revolutionized by the discovery of a Coptic Gnostic library at Nag-Hammadi, Egypt. Currently, Gnosticism is seen as a phenomenon extending far beyond Christianity and displaying a strong Platonic influence. The opposition between the two systems was certainly not as sharp as Plotinus claimed. Where, why, and how the ideological lines were drawn is discussed in the light of the new historical evidence.