Biblically speaking, we are creatures. And life as a creature means that our existence is a dance between sunlight and shadows. Positively, we name our existence as good. Negatively, we see and experience how our existence is unstable. We are prone to damage, disease, decay, and death. And when our finite contingency intrudes, when existence is eroded, we name that as evil.
When we talk about the problem of evil some break it down into categories. Moral evil and natural evil is one contrast. Moral evils are the harms humans perpetrate against each other. Natural evils are the sufferings intrinsic to the human condition, from diseases to natural catastrophes to untimely accidents.
Since moral evil is caused by human agents some set God's responsibility aside in these cases. Moral evil is a self-inflicted wound, and if humanity would stop hurting itself such evils would go away. Natural evil presents a different case, for even if moral evils ceased to exist cancer and natural disasters would still be with us. Regardless, in both instances, our finitude is implicated. As creatures we are vulnerable to harms. And when those harms come, moral or natural, we name them as evils.
Experientially, this makes total sense. If existence is a positive good then anything that erodes our existence is the opposite of good. Augustine famously described evil as privatio boni. Evil has no positive existence but is, rather, the privation of the good. For finite creatures, evil is the loss of existence, the erosion of being. As we see our being dissolving, slowly or in a moment, we name our dissolution as evil.
The "problem of evil," therefore, is entangled with our existential posture toward finitude. By definition, finite existence fades into non-existence. Which means that evil is an intrinsic aspect of finite existence. Evil isn't an ontological intruder. Our tendency toward non-existence, what we name as evil, is simply what it means to exist as a creature. Evil is an ontological implication of finitude. That is, to exist is to experience evil.
Thus, to raise a question about evil is to raise a question about existence itself. If you ask "Why is there evil?" the answer is straightforward: "Because you exist." If you exist, as a creature, you will be shadowed by non-existence. That's what it means to exist as a finite, contingent being. Consequently, any sort of surprise or outrage we experience about evil flows out of a confusion (or delusion) about the nature of creaturely existence. In this sense, the question "Why is there evil?" is odd. The question betrays a lack of ontological insight.
Of course, if this insight was grasped and appreciated a follow up question could be asked. "Fine, I see your point. Evil is simply a name for the ontological consequences of finitude and contingency. If so, then why didn't God make me a self-subsistent, infinite, necessary being? A being immune to non-existence?" The answer, though, is obvious. If we are created, by definition, our existence cannot be self-subsisting, infinite, or necessary. Theologically, this is what the doctrine of creation ex nihilo is getting at, how our existence is finite and contingent and that there is no other kind of existence outside of God's own aseity. Ontologically, there is God and there are creatures, and we are creatures. So, the question above becomes, "Then why didn't God make me God?" And that question seems to answer itself. For to be "made" rules out you being God.
Now, you may be starting to ask some questions here. Isn't the theological claim of Genesis that creation is intrinsically good? If so, it seems like I'm suggesting here, contra Genesis, that creation might be intrinsically subject to evil. To wrestle with this issue we need to wade into how creation relates to finitude in light of the Fall.
We'll turn to that issue next.
