Full Idea
We must believe that God would not have allowed sin nor would he have created things he knows will sin, if he could not derive from them a good incomparably greater than the resulting evil.
Gist of Idea
God only made sin possible because a much greater good can be derived from it
Source
Gottfried Leibniz (Dialogue on human freedom and origin of evil [1695], p.115)
Book Reference
Leibniz,Gottfried: 'Philosophical Essays', ed/tr. Arlew,R /Garber,D [Hackett 1989], p.115
A Reaction
Why 'must' we believe this? Do we have to imagine all the genocides shrinking to insignificance once we grasp the wonderful goods that can be derived from them? The end justifies the means. Genocide is actually a good thing. Hm.