Gnosticism is a modern umbrella term for diverse religious movements of the early Christian centuries that emphasized a saving knowledge or gnosis.
Common themes
The systems differed greatly, but many sharply separated the supreme God from the material cosmos, described layers of spiritual intermediaries, and regarded salvation as awakening to a hidden divine identity or origin. Some forms treated embodiment and material creation as defective or hostile.
Christian response
Writers such as Saint Irenaeus defended the public apostolic proclamation, the unity of the Old and New Testaments, one Creator, the true Incarnation, bodily resurrection, and the continuity of faith preserved in the churches founded by the Apostles.