I agree with ben d. Enlightenment is a realization of non-duality; a unity with the screen upon which the universe is projected. It is not "knowledge," it's more like a seizure.
Enlightenment's primarily an Eastern concept, foreign to the Abrahamic traditions. When a Christian or Muslim speaks of enlightenment s/he's talking about something entirely different from the "standard" eastern, or the western, Huxleyan conception.
Of course, considering it in the context of a psychosis or a temporal lobe status epilepticus, it's bound to pop up periodically in all populations, regardless of religious tradition, as Huxley pointed out. Christians tasting it have had to take great care to couch their descriptions in proper eccliastical language to avoid charges of heresy.