Blackmailing the universe

This quote is today's entry in The Business of Heaven, which is a book of daily readings of C.S. Lewis quotes. The endnotes say this comes from Great Divorce, chapter 8:

'What some people say on earth is that the final loss of one soul gives the lie to all the joy of those who are saved.'

'Ye see it does not.'

'I feel in a way that it ought to.'

'That sounds very merciful: but see what lurks behind it.'

'What?'

'The demand of the loveless and the self-imprisoned that they should be allowed to blackmail the universe: that till they consent to be happy (on their own terms) no one else shall taste joy: that theirs should be the final power; that Hell should be able to veto Heaven.'

'I don't know what I want, Sir.'

'Son, son, it must be one way or the other. Either the day must come when joy prevails and all the makers of misery are no longer able to inflict it: or else for ever and ever the makers of misery can destroy in others the happiness they reject for themselves. I know it has a grand sound to say ye'll accept no salvation which leaves even one creature in the dark outside. But watch that sophistry or ye'll make a Dog in a Manger the tyrant of the universe.'