When dealing with the question, "what is evil", we believe we first must determine if evil is something that "exists" independently or not. In other words, does evil have its own being? It would be impossible to state that moral and metaphysical evil exists on its own, apart from the presence of good.
We would therefore argue that evil is not something that has its own existence or "being" in the sense that God has "being". God alone (as did Christ) could say "Before Abraham was, I AM. God is infinite in His "being" whereas evil has not this measure of existence and is therefore not something that has inherent "being".
Evil is instead, an activity of a being.
What is a being? Whether we mean an eternally subsistent creator/being (God is an eternal being) or a created person (man and angels are beings in a created sense), this is a "being" that can do activities good and evil, though God does not do evil. So in a sense, evil has no essential being in itself, apart from those who do it. By the way, Christian Science (which is neither christian nor science) errs here in that thinking that since evil/sin has no inherent "being" in itself, that evil is somehow an illusion. But we find all around us that living beings act out that which is evil and it has had an ongoing and devastating impact, none of which are illusions. Calling good evil and evil good, is in itself evil and is called sin in the Bible. Isaiah 5:20 says:
Woe to those who call evil good, and good evil.
But what then is evil if it has no "being" in itself, but is instead the actions of those who have a finite created existence or "being"?
Defining evil is best done by a method commonly used in educating, that of contrast. By contrasting something with that which is good, helps identify evil since good is a characteristic of the eternal God and evil would be the antithesis of such. Here are some terms whose prefix explore this type of contrast:
Evil is seen in contrast with good, and is like a parasite, which is not known in and of itself, but is only known and understood in the context of the good or positive standard. For example, this term "parasite" would tell us that if the host dies, the parasite dies in like manner. It is only defined and explained in the presence of that which is good- the host.
Another way of thinking is that evil is a lack or deficiency of something needed (not something wanted, but needed - very different). It is evil that children die of hunger. Or evil is that which happens as in the typhoon that kills thousands.
Sin is a measurement of evil, and ultimately should be defined as a lack of conformity to, or transgression against, the character or revealed will of God. Man's failure to conform to God's declaration of righteousness (for example, in the Law of Moses), is an expression of evil/sin. It is "seen" in the context & presence of that which is good and righteous.
If we contrast that which is good, noting that God is a good, transcendant, self existent person/being, with that which occurs that is contrary to Him, we find something that is an antithesis to good; namely, evil.
Yet how could evil intrude or be expressed into a universe of a God who is altogether good, righteous, and omnipotent? This moves us from the question of defining evil, into the question of the origin of evil. How can God allow it, and for that matter from where does it come? We could say from Satan, or from Free Will, but neither explain its origin but rather its earliest proponents.
Where does evil come from? We will honestly state that we do not know because it has not been revealed. Insufficient explanations have been given from these two extremes, the first of which best approaches where we must stand, though without being a real final explanation:
God created it for His glory and has not told us why.
Free will of man was given by God. While this is true about man's will, it does not adequately explain things because to choose the evil implies an inclination to disobey in the first place, and does not explain how/why the serpent was allowed to do so, etc. Where does the evil inclination come from - - remains unanswered.
The question of where does evil come from, to really answer it, demands an adequate ability to stand in a position of full knowledge. But man does not have this ... and in trying to answer such questions high above his intellect and wisdom, and knowledge (and apart from revelation), he must set himself above God as an arbiter and judge in the matter of why something like evil can take place. In other words, for a creature (man) to explain (or demand knowledge of) the origin of evil and complain about why it exists, he has to be in the position of God to do so. If he does so, he sets himself, equal to or above God in his thinking (which is basically something like "it should not exist!"). Pondering the existence of evil is one thing, demanding that it should not exist as if I were the deity in charge, is another matter indeed, and is self exaltation.
This exaltation of self was the act and mind of Satan as seen in Isaiah 14:
12 “How you are fallen from heaven,
O Lucifer, son of the morning!
How you are cut down to the ground,
You who weakened the nations!
13 For you have said in your heart:
‘I will ascend into heaven,
I will exalt my throne above the stars of God;
I will also sit on the mount of the congregation
On the farthest sides of the north;
14 I will ascend above the heights of the clouds,
I will be like the Most High.’
If we go even farther back to the Bible and the entrance of evil into the sphere in which man dwells-earth, one may ask why did God give that one prohibition to man, in Genesis 2:
16 “Of every tree of the garden you may freely eat; 17 but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die.”
Here are two"innocent" beings, unfallen, and what is put before them is the one prohibition against doing what is "evil". How can this be? Why even have a prohibition where there is innocency? Obviously the temptation itself was an evil perpetrated by the serpent, yet it is not explained....why.
Ultimately, the problem is we have not been told why there is evil, nor where it comes from. We can determine much of what is evil by comparing everything to the revealed character and will of God in scripture. Yet the question of why & where it comes from, requires from us, what we do not have. We are not Deity.
Genesis 50:20 gives a perspective from the life of Joseph where we approach the good results of the allowance/presence of evil, without being able to ultimately answer why. Here was the prime minister of Egypt, answering his own estranged brothers who long ago meant him great evil by selling him into slavery, yet he could say, with great power now behind him:
But as for you, you meant evil against me; but God meant it for good, in order to bring it about as it is this day, to save many people alive.
Also for the heart to ponder is higher ground: Who ultimately delivered up Jesus to the Gentiles to be killed per Isaiah 53:10?
Yet it pleased the Lord to bruise Him;
He has put Him to grief.
When You make His soul an offering for sin,
He was the sacrifice slain (in the counsels of God) even before the foundation of the world, and that is staggering.
God has therefore ordered a universe where evil exists in the actions of those who are created, finite beings. And we do not know ultimately why. We would be wise also not to charge God with creating evil (see postscript below).
Dealing with the reality of evil and sin is another thing. We do have before us many glories to ponder even in the presence of evil. These include overcoming, redemption, salvation, etc. Our inability though, to explain it all, is because we are creatures, and to answer it adequately we would have to be Creator.
The reality is that the presence of evil in the world in which we live, points to the existence of good. So in our creaturely state, this is good for us, is it not?
The atheist (and pagan) as he would seek to challenge Christianity on this very question, has a more difficult problem than he admits, as he must not only answer the question "why is there evil," but he must answer therefore also, "why is there good?" (and ultimately his real conundrum and end result is that he cannot say there is good or evil).
Steal something from such an one (the atheist or pagan) that is important to him, and he will quickly abandon his relativism, and he will call the police and agree that this was wrong and that there is evil, though he may couch it in other terms.
He cannot answer the question of evil or good, at all. He merely argues against the existence of evil, "if God is good and all powerful, why does He allow evil? If He is good, it should not exist, if it exists and He cannot stop it, He is not God" And so it goes.
But such a person does a dangerous thing, in placing himself, a creature, above the Creator, and doing so stands (so he thinks of himself as Lucifer-exalted) and puts himself into an exalted position as JUDGE when he as a creature...with insufficient wisdom, information, and goodness of his own. It is a self defeating argument. And we find too, that in the end, the strongest arguments against "God" from such persons, usually have behind them a desire to continue in behaviors, that such a God says are.....evil.
We must trust the Lord and admit, we do not know, with our incomplete knowledge, incomplete intellect, incomplete wisdom, and remember to trust Him whom we have come to know as being Good indeed:
Revelation 21:4 And God will wipe away every tear from their eyes; there shall be no more death, nor sorrow, nor crying. There shall be no more pain, for the former things have passed away.”
The former things. What a lovely thought. Passed away.
Isaiah 45:6-8 in the KJV, uses the term "create" and gives the impression that God is the author of evil:
6 that they may know from the rising of the sun, and from the west,
that there is none beside me.
I am the Lord, and there is none else.
7 I form the light, and create darkness:
I make peace, and create evil:
I the Lord do all these things.
8 Drop down, ye heavens, from above,
and let the skies pour down righteousness:
let the earth open, and let them bring forth salvation,
and let righteousness spring up together;
I the Lord have created it.
Here we quote in part a good answer give by gotquestions.org on this passage and the notion of God "creating" evil:
"...two key facts.... (1) The word translated “evil” is from a Hebrew word that means “adversity, affliction, calamity, distress, misery.” ......The Hebrew word can refer to moral evil, and often does have this meaning in the Hebrew Scriptures. .but... (2) The context of Isaiah 45:7 makes it clear that something other than “bringing moral evil into existence” is in mind. The context of Isaiah 45:7 is God rewarding Israel for obedience and punishing Israel for disobedience. God pours out salvation and blessings on those whom He favors. God brings judgment on those who continue to rebel against Him... So, rather than saying that God created “moral evil,” Isaiah 45:7 is presenting a common theme of Scripture – that God brings disaster on those who continue in hard-hearted rebellion against Him."
In other words, God created the consequences that befall them that do evil.
much of the logic of the above thinking but not all, attributed to an online message by RCS on the problem of evil.