Arguably the second oldest and most persistent Christian heresy is gnosticism (the first is legalism). Early forms of it were condemned in Colossians and possibly other Pauline letters, and also in 1 John. Gnosticism splits the “spiritual” world from the visible material world, saying that what really counts is not what we can see, but only what happens in the invisible realms. It seriously undermines God’s work in creation and especially in the Incarnation and Resurrection. It violates clear biblical teaching about the end times, the future state we call “heaven.”
Gnosticism is not Christianity.
Harold Camping says Judgment Day actually did happen last Saturday—in a “spiritual” sense. Can his teachings still be called Christian? Some of them, yes. But his most public ones are infected with deadly error.
I don’t want to draw the Gnostic connection more closely than it deserves, but it comes to mind that Gnosticism tends to promote spiritual pride, and vice-versa. One wonders if some humility might have helped Camping admit he made a mistake.