Full Idea
There is a contradiction between the propositions that God is wholly good, God is omnipotent, and evil exists, and one of them has got to give way (assuming good eliminates evil, and omnipotence has no limit).
Gist of Idea
The propositions that God is good and omnipotent, and that evil exists, are logically contradictory
Source
report of J.L. Mackie (Evil and Omnipotence [1955], Pref.) by PG - Db (ideas)
Book Reference
'The Philosophy of Religion', ed/tr. Mitchell,Basil [OUP 1971], p.92