Full Idea
Augustine solution to the problem of evil was to say that, strictly speaking, evil does not exist. Human beings are not part evil and part good, but rather just a limited amount of goodness.
Gist of Idea
Augustine said evil does not really exist, and evil is a limitation in goodness
Source
report of Augustine (works [c.415]) by Franklin Perkins - Leibniz: Guide for the Perplexed 2.III
Book Reference
Perkins,Franklin: 'Leibniz: Guide for the Perplexed' [Continuum 2007], p.44
A Reaction
Augustine was rebelling against Manicheanism, which he espoused when young, which proposed a good and an evil force. An apathetic slob seems devoid of goodness, but is not evil. It takes extra effort to perform active evil.