From Karen Armstrong’s A History of God: The 4,000-Year Quest of Judaism, Christianity and Islam:

Although it is clearly culturally conditioned, this kind of “ascent” seems an incontrovertible fact of life.  However we choose to interpret it, people all over the world and in all phases of history have had this type of contemplative experience.  Monotheists have called the climactic insight a “vision of God”; Plotinus had assumed that it was the experience of the One; Buddhists would call it an intimation of nirvana.  The point is that this is something that human beings who have a certain spiritual talent have always wanted to do.  The mystical experience of God has certain characteristics that are common to all faiths.