The Christians say that evil is not a force or a power or real. Their faith says that evil does not inhere in things but is something that needs good to corrupt for it has no value or power of its own. The believers refer to intrinsic evil but that does not make sense. Why not say intrinsic nothing?
All evil is, is good that is not good in the right way. It is good in the wrong place and time. It is a lack. Just as space, in theory, could be the lack of something and is nothing.
The thinking behind that is that good is about existence. Existence and being real are good. In other words, something that exists is good for existing. Merely being there is good. We are talking about good that is metaphysical or intrinsic.
Another idea that follows from all that is that if you are a bad person then as far as you exist you are good. Nobody thinks a person sitting on a couch is being good for just sitting there. What matters to everybody around is that this individual gets up and helps others. It seems a God could permit that person to do nothing but the only reason the person should do good is that God has set up society, the community of people who need each other and need to help each other. The ugly thing there is that sounds like a mere extra, an afterthought. It is not a glowing endorsement of goodness. God is in control anyway so as he is in charge he might do the good for us that we don't do.
To be an evil person you have to be an existing one first and foremost. It is a contradiction to call you evil if you are good for merely existing. You can at most water down the badness by saying it is only a small facet of the person. So sending the rapist to jail is an evil.
If good is existence then evil is that which tries to make good cease to exist. Even if a good thing is ruined it still exists and is not destroyed completely but evil is bad for it tries to make it cease to exist. If creation makes, then evil tries to do a reverse-creation and un-creation. More evil means less existing.
If you believe in God then God being that which exists of himself. He receives his being or existence from nothing else. So for that reason, we are told, only God is absolute total good. We are told that God is the reason for his own existence and the universe is made by him of his own free will by his mere command - creation. Evil as in falling short of being better or good is only happening because nothing can be perfect unless it is God. Which it is not.
As everything is imperfect it surely inspires us to be imperfect on purpose or sinful. Imperfection is the very stuff of life and living. We all have, "If I cannot beat it I will join it" written in our DNA.
Religion would say. "Moral evil is like a wound and it is perversion. Moral evil is a perversion of your nature. It is to be hostile to your nature and to try to destroy it and kill it. God controls our evil but he does not cause it or love it or in any way approve of it." That does not relate to what we know of reality and nature.
Religion says the evil in us that makes us cruel and deceitful and unjust does not come from good but depends on it. Good has to exist and only then is it possible for any falling short as in evil to take place. Evil is good in the sense that it shows the thing could be so much better and should be. Evil can only hurt what is good so it bears witness to goodness. If a villain hands you the number of the local police station he is not a villain but a fool. Faith is redefining evil as stupidity and mistakes and retaining the word evil.
An eye is meant to see. If it does not see that shows it should. So if you fail to see how evil despite itself supports good you need to be aware of that. Thus if you see the evidence of evil you have to hold that you are suffering some kind of moral blindness. Religion says that natural or moral evil is good in the sense that it is good in the wrong place and time and not good enough. It judges this as being related to a bad intention. Its morals tell it if there is any doubt assume the person meant well. The whole point of moral theology and ethics collapses if we are to start seeing what one would take to be evil as a messed up attempt to do good. Such an idea will lead to you giving up on good works.
It should be easy to see a person who is doing grave evil and harm for complicated reasons as confused but meaning well underneath it all. It is not. We will hate that person. Religion has to be lying about its unconditional love for that person.
We have said that the universe is not God so it has to have defects and we can describe those flaws as natural evil. Natural evil in religion is not considered to be real evil but just a heap of deficiencies. Real evil is considered to be both wanting to do harm and to attack moral good which involves love and justice and mercy. Natural problems are not good nor bad in the ethical sense, but simply non-moral or neutral. Natural evil needs to exist before moral evil as in the rejection of love justice and mercy can be possible. To abuse you need something that can be abused in the first place.
The claim that God made the universe and nature good suggests that sin or deliberate harming is unnatural. That is insane for deliberate harming is definitely natural. If an animal is tormented to death by predators the suffering is the point not if the predators were intentionally harming or not.
It does not follow that all things being good means that one thing is as good as another. An overcooked dinner is not as good as a properly cooked one. No natural thing is as good as God therefore there is a built in imperfection - a failure to be as good as it can be. If creation has to be imperfect and make imperfect things and imperfection paves the way for the possibility of evil then it follows that evil is necessary. It is as natural for a man to kill another for fun as it is for a bee to carry pollen.
Natural evil is supposed to be different from moral evil. So what? They could still be married. If evil lies and hides itself amidst good it will fool us that natural evil is not evil. It is natural evil that makes moral evil possible. We are natural creatures so the natural evil in us is married to the moral evil in us. They are married in us and by us with us as the celebrants. Nobody can tell how much natural evil was a part of the moral evil they did. We have animal instincts so we will do what animals do, harm.
Sin cannot exist except in a person and as part of a person. It is in the person's will and intentions. It is not a mere abstract. It It is thus not the same evil as natural evil at all. But that does not matter. Evil is evil. It owns natural evil.Evil an
d sin are two related but different ideas. Sin is seen as breaking the divine law of love with full knowledge and full consent. While all sin is evil all evil is not sin. A person who had no concept of law can do harm for fun and that is evil but not sin.
A theist may say that metaphysically speaking, evil is a lack, a negation, a nothing. But may say that morally and ethically it is positive, a thing, a reality. That is just confused and clearly wrong. It is still saying evil is nothing but to our minds it is very much anything but. We all know that already. It is why we feel that we don't like being told that our pain and suffering are so horrid for they act like they are real when they are not and we blame our own perceptions.
For St Augustine as for Christianity, the reason things fall short of being truly good is because all things are made from nothing. What does the origin of things have to do with it? Nothing can be as good as God so limitations and defects are going to be there. The doctrine that free will is a gift from God makes little sense. If he cannot create anything perfect then if he gives a will to us it has to be free to be good or defective. Free will in this sense is no gift and no affirmation of dignity. It is a side-effect. If that is all it is, it is asking to be abused. The God who gave it is as good as asking for it.
Christianity following Jesus and the likes of St Augustine alleges that as we have free will and can abuse it, we cannot say there is any evidence that free will shows that God is in any way bad. That is a lie. Why? Free will is bearing too much bad fruit so that is evidence. Also, it is overplaying to argue that free will would show the higher power is in no way bad at all. A tolerable level of evil in the deity could be considered.
The idea that what is not a God must be imperfect denies the Christian doctrine that in Heaven there is only good and no evil.
FINALLY
Religion cannot get its account of what evil actually is straight. If the whole point of faith in a good God is so that you may be good and avoid evil then that point is overthrown. That would weigh heavily in favour of atheism and its value.
If creation were an unorganised chaotic mess it would still be good for it exists. It cannot be called evil. The first thing that pops up with this is that if God wanted to create that way that would be his right. But it would mean this God is not really relevant to us. We want an orderly sensible one that looks after us. He treats us as an option, a project. As he is not real, the ones objectifying us as projects are his followers.