Inconceivable, appalling

He said, ‘There was a man, a Frenchman, you wouldn’t know about him, my child, who had the same idea as you. He was a good man, a holy man, and he lived in sin all through his life, because he couldn’t bear the idea that any soul could suffer damnation.’ She listened with astonishment. He said, ‘This man decided that if any soul was going to be damned, he would be damned too. He never took the sacraments, he never married his wife in church. I don’t know, my child, but some people think he was—well, a saint. I think he died in what we are told is a mortal sin—I’m not sure: it was in the war: perhaps…’ He sighed and whistled, bending his old head. He said, ‘You can’t conceive, my child, nor can I or anyone the… appalling… strangeness of the mercy of God.’

— Graham Greene

Also, nested colon clauses.