True evil is to choose one good to the exclusion of another good when it is clearly evident that the good excluded is far superior.
For example, one might commit suicide to end the pain when existing, even with pain, is far superior.
Or, one might overeat, appreciating the feeling of comfort that food provides, when good health is far superior.
Why would anyone do this (or make any other similarly erroneous choice)?
I honestly have no idea, but I do it all the time…
As for the question, ‘Why would a good god create a world where this is possible?’ See the original post and related Discussion.
Root Page: The Problem of Evil
The Holiness Project 