Full Idea
If a Creator is assumed to be omnipotent, if he bends to a supposed necessity, he himself makes the necessity which he bends to. If the maker of the world can all that he will, he wills misery, and there is no escape from the conclusion.
Gist of Idea
No necessity ties an omnipotent Creator, so he evidently wills human misery
Source
John Stuart Mill (Nature and Utility of Religion [1874], p.119)
Book Reference
'The Existence of God', ed/tr. Hick,John [Macmillan 1964], p.119
A Reaction
If you add that the Creator is supposed to be perfectly benevolent, you arrive at the paradox which Mackie spells out. Is the correct conclusion that God exists, and is malevolent? Mill doesn't take that option seriously.