The Logical Problem of Evil
Lewis Carroll opens "Jabberwocky" like this:
'Twas brillig, and the slithy toves Did gyre and gimble in the wabe; All mimsy were the borogoves, And the mome raths outgrabe.
The first time I read that poem, I got about two lines in before I thought, "okay, there are some words here I need to look up." By about ten lines in, I'd finally figured out the truth: there was nothing to look up. Carroll made the words up. But here's the strange thing—the poem doesn't read like nonsense. It's not a cat walking across a keyboard. It has grammar. It has rhythm. It has a plot, for crying out loud (there is, in fact, a monster, and someone does slay it). It reads like it should make sense, and yet it doesn't quite.
I think that's the best description I know of what evil feels like from the inside. The world isn't chaos. There's a way things are supposed to go. And yet, every so often—more than every so often—something shows up that looks like it wandered in from a different poem entirely. A child gets cancer. A genocide happens. Someone commits an atrocity so far outside the bounds of "the way things should be" that we don't even have adequate words for it. The world reads like it should make total sense, and then there's evil, sitting right there in the text, refusing to parse.
That gut-level sense that evil doesn't belong is exactly what gets turned into a formal argument against the existence of God. This is the argument I want to introduce today: the logical problem of evil. It's the granddaddy of all the arguments in this series, and honestly, understanding it well is the key to unlocking almost everything else we'll talk about in the coming months.
Three Kinds of Problem
Before we get into the argument itself, I want to make a distinction that I think gets lost a lot in these discussions. When people say "the problem of evil," they could mean at least three different things.
There's the logical problem of evil—this is the version you'd encounter sitting in a classroom, calmly working through premises on a whiteboard. It's abstract, it's academic, and it's what we're doing today.
There's the evidential problem of evil—this is a step removed from pure logic. It's less "evil logically disproves God" and more "given how much evil there is, and how pointless so much of it seems, it's just not reasonable to believe God exists." We'll get to this one down the road.
And then there's the existential problem of evil, and this one is a completely different animal. This isn't a seminar question. This is a person in the middle of unbearable suffering asking, "why is this happening to me?" I want to be honest with you: I've watched a close friend lose his wife to cancer. I couldn't imagine sitting across from him in that moment and saying, "well, here are some good philosophical reasons why this happened." That would be monstrous. If you're in the middle of real suffering right now, please don't mistake anything I say in this series—or this post—as an attempt to explain away your pain. What I say might still be useful to you eventually. But if you and I were sitting across from each other right now, we'd be having a very different conversation.
With that said, let's do the philosophy.
The Argument
The logical problem of evil, in its classic form, goes something like this:
- If God exists, God could prevent evil.
- If God exists, God would prevent evil.
- So, if God exists, evil doesn't exist.
- Evil exists.
- Therefore, God doesn't exist.
Let's take these one at a time, because each premise is doing real work.
Premise 1 rests on two of God's classical attributes: omniscience (all-knowing) and omnipotence (all-powerful). Consider Katie Kyser, a woman who—like far too many people—developed cancer that doctors simply didn't know how to cure. That's a limitation of knowledge. We didn't know how to stop it. But God, by definition, knows everything. He wouldn't have that limitation. He'd know exactly how to cure any cancer, instantly, because there's no fact about biochemistry or cellular mutation that could be hidden from an omniscient being.
But knowing how to fix something isn't the same as having the power to do it. Think about a miscarriage. It's not that we don't know, in principle, what it would take to reverse it—it's that we have zero power to do so. We're just not strong enough, cosmically speaking. God, though, is supposed to have created the entire universe out of nothing. If you can speak galaxies into existence, reconstituting a miscarried child should be trivial. Even if you reject the classical "creation from nothing" view and think God merely rearranged pre-existing material, an all-powerful being should still be able to rearrange the material of a human body. So: if God exists, He could prevent any evil, because He'd know how and He'd have the power.
Premise 2 brings in the third classical attribute: omnibenevolence (all-good). Here's a silly but useful way to think about it. There's an old Seinfeld bit about how nobody actually wants to help anybody move—moving is the ultimate test of friendship, because there's a cost to you and no real benefit. But suppose helping cost you nothing at all. Suppose you could stop your friend's disaster with a snap of your fingers, at zero risk or cost to yourself. At that point, refusing to help isn't neutral anymore—it just makes you a bad person. If you can effortlessly prevent suffering and you don't, that's on you. God, ex hypothesi, can prevent evil at literally no cost or risk to Himself. So if He's genuinely all-good, He would prevent it.
Premise 3 just follows logically from 1 and 2 (with an assumed premise that a being who both could and would do something, does it).
Premise 4 is the empirical claim, and it's the Chesterton point I opened with. G.K. Chesterton wrote in Orthodoxy (1908) that "the real trouble with this world of ours is not that it is an unreasonable world, nor even that it is a reasonable one. The commonest kind of trouble is that it is nearly reasonable, but not quite." That's the Jabberwocky world. People shouldn't suffer the way they do. Babies shouldn't get cancer. There shouldn't be genocide. And yet there is. Evil isn't merely a philosophical abstraction—it's a fact about the actual world we live in.
Premise 5 follows by a rule of logic called modus tollens: if God's existence entails no evil, and evil exists, then God doesn't exist. (If you want the formal logic behind this, worth digging up any decent intro logic textbook—the rule is one of the most basic and reliable in the whole discipline.)
Where This Argument Came From
This precise formulation has a real history. The philosopher most responsible for popularizing the logical problem of evil in its modern form is J.L. Mackie, an Australian philosopher who published a paper called "Evil and Omnipotence" in the journal Mind in 1955. Mackie argued that the existence of evil creates a genuine logical contradiction with the traditional theistic claim that God is omnipotent and wholly good—not just evidence against God, but an actual formal inconsistency. This was a big deal. For a while, it was considered maybe the single strongest argument against theism in the philosophical literature.
But here's something I want to be upfront about: the logical problem of evil, in Mackie's strong form, has been pretty thoroughly answered. I don't say that to be dismissive of atheism or to declare victory—there's still the evidential and existential versions to reckon with, and those are much harder to wave away. But specifically as a logical argument—a claim that evil and God's existence are strictly, logically incompatible—it doesn't really hold up anymore, even among many atheist philosophers of religion.
The person most credited with dismantling it is Alvin Plantinga, an American philosopher who, in works like God, Freedom, and Evil (1974), developed what's called the Free Will Defense. Plantinga didn't try to prove that God does have a good reason for allowing evil. He only had to show it's possible that God has a morally sufficient reason—maybe something to do with the value of creatures having genuine free will—for allowing the evils we see. If it's even possible, then premises 1 and 2 aren't as airtight as they look, and the "logical contradiction" Mackie claimed to find evaporates. Even the philosopher William Rowe, an atheist, conceded that Plantinga had succeeded in showing the logical version of the argument doesn't work.
That's the big move that separates the logical problem from the evidential problem: the logical version claims it's impossible for God and evil to coexist. The evidential version is more modest—it says that given how much evil there is, and how gratuitous so much of it seems, it's simply unreasonable to keep believing in God. That's a much tougher argument to dismiss, and we'll spend real time on it later in this series.
So What's Actually Wrong With the Premises?
If the logical problem has been "pretty well answered," that means at least one of premises 1, 2, or 4 has some hidden assumption we should be suspicious of. As it turns out, there's a whole family of responses—coming from wildly different theological traditions—that each attack a different assumption buried in this argument. Some reject the assumption that God, if He exists, must be omniscient in the way we usually think. Some reject the assumption that God must be omnipotent in the classical sense. Some even question whether evil, understood the way the argument assumes, really exists at all.
Over the next several posts (and videos), we're going to walk through each of these responses one at a time: Open Theism, the LDS view of a non-omnipotent God, the Hindu response that treats evil as illusion, and several others, before turning to the reasons a classical theist like myself thinks God allows evil in the first place.