From Howard Elseth’s Did God Know:
The term sums up the common qualities of a certain class of actions. If we use the word goodness as a synonym for God, we must remember that God is good because He chooses to be good. If we say that God is simply a “blob” of good in the sky who can do nothing but good, because He is good, you then destroy the factor of choice. If you eliminate choice you eliminate virtue. This would make God no different than a machine operating out of necessity in proportion to the quality of its construction and the ability of its operator. Similarly in regard to evil. It is not a concrete thing, but an abstract term. It represents the common qualities of a certain class of actions. Evil exists because beings choose to sin. So the problem we must face is this: Is God responsible for the evil acts of these beings? If not, who is?