Here is the closing bit of the essay:
There is, though, a third possibility, the one that I want to end on because it seems to me potentially the most interesting, though perhaps the most daunting. This is that the religious fanatic is someone for whom something about themselves and their lives is too much; and because not knowing what that is is so disturbing they need to locate it as soon as possible. Because the state of frustration cannot be borne – because it is literally unbearable, as long-term personal and political injustice always is – it requires an extreme solution.
In this account our excessive behaviour shows us how obscure we are to ourselves or how we obscure ourselves; how our frustrations, odd as this may seem, are excessively difficult to locate, to formulate. Wherever and whenever we are excessive in our lives it is the sign of an as yet unknown deprivation. Our excesses are the best clue we have to our own poverty, and our best way of concealing it from ourselves.