Full Idea
Moral evil may be acceptable to a benevolent God because it is the only way to allow genuine free will, which may have a supreme value in creation (even if we are unsure what it is).
Gist of Idea
Moral evil may be acceptable to God because it allows free will (even though we don't see why this is necessary)
Source
report of Alvin Plantinga (Free Will Defence [1965], Pref.) by PG - Db (ideas)
Book Reference
'The Philosophy of Religion', ed/tr. Mitchell,Basil [OUP 1971], p.106