Sometimes history can shed a little light on the present.
If I understand it correctly, the philosophy of Gnosticism can be summed up as “spirit is good, matter is bad.” They viewed the material world as a prison from which we should seek release. Gnostic Christianity was an attempt to blend this view with Christian teachings.
The result was a variety of views that contradicted mainstream Christian teaching. One taught that Christ did not have a physical body, another that Jesus was just a man infused with the Christ-spirit. Still another said Jesus’ physical body died to release his spirit from the material realm.
Of course, if matter was bad, a physical resurrection – for either Jesus or us – was not a desirable thing, so they spiritualized the gospel to be enlightenment and freedom from the physical world.
Though they had access to the Jewish and Christian writings, they rejected most of these and created their own. After all, if the physical world was bad, anything that suggested that Jesus, or the Father, had a hand in creating it wouldn’t work. Some even taught that the God in Genesis was a different god from the Father of Jesus.
How did this lunacy come about? People took the philosophy of their day, Gnosticism, to Christianity rather than getting their philosophy from it. Despite what Christian texts said, their philosophy said matter was bad, so they had to reinterpret the gospels and the gospel to get a religion than made sense to their philosophy. And wackiness ensued.
If I understand it correctly, the philosophy of postmodernism in a nutshell is a radical skepticism about our ability to discern what is true. As people take this philosophy to Christianity, perhaps the Gnostics can serve as a warning. Not all human philosophies are fatally flawed, but we should be more skeptical about the tenets of the philosophy du jour and how it can relate to a religion that has been ironed out over the course of two millennia.
Already there is a great deal of concern over the church that is emerging from the fusion of postmodernism and Christianity. This task requires caution and a great deal of humility about more than just epistemology.