One of life's great mysteries... (btw, it's a fantastic episode) 

Interesting fact: Religious people who have NDEs become more religious. Non-religious people who have NDEs don't become more religious.

Interesting fact 2: a NDE is near death. It's not death. You can't have one and say "The last time I died..." (I've been caught saying that in the past, but not to an audience smart enough to realise it's just word play).


Never seen a better explanation than that offered by Susan Blackmore.