Culdee philosophers came to see that evil isn't some active power, force or thing, but rather absence of power, force or thing.

God, The One, The Good, The Beautiful is self subsistent. Like the One in arithmetic doesn't need the two, three or four to subsist, because it isn't contingent on any other number, God has no need of anything to subsist.

On the other hand, the two, three, four, and so forth, are necessarily contingent on the existence of the One. In the same way all that exists is contingent on God.

Evil can only be said to exist relative to something. It is never self subsistent and always contingent. It is contingent on whatever something to which it is relative. The relation evil has with things is absence. In general it is absence of the Good, but in particular it is the absence of something that perfects the thing to which it is relative.

Examples might be sins like murder, theft, adultery, coveting and so forth. Each one can be shown to have its basis in a lack. Generally the lack is ignorance, or the absence of knowledge. In general the perpetrator is doing something we are all doing all the time. He is attempting to attain or maintain a degree of happiness. The murderer thinks that he will attain greater happiness by killing another person for revenge, gain or something else. The thief thinks he will attain greater happiness through easy gain. They are ignorant of the fact that they are not the owner of either the other person or any other temporal thing. They have no true control over people or things. They don't even have true control over their own body, or possessions. Their bodies will become sick despite their desire for them to be well, and they will die despite wanting to live. Their possessions will wilt and wither, crack and leak and they inevitably won't be able to stop the entropy.