Here's a sequel to my post in Inwagen:
Among other things, he says:
But an omnipotent and omniscient creator could be called to moral account for creating a world in which there was even one horror. And the reason is obvious: that horror could have been "left out" of creation without the sacrifice of any great good or the permitting of some even greater horror. And leaving it out is just what a morally perfect being would do: such good things as might depend causally on the horror could–given the being's omnipotence and omniscience–be secured by (if the word is not morally offensive in this context) more "economical" means. The Problem of Evil (Oxford, 2006), 96.
A defense cannot simply take the form of a story about how God brings some great good out of the evils of the word, a good that outweighs those evils. At the very least, a defense will have to include the proposition that God was unable to bring about the greater good without allowing the evils we observer (or some other evils as bad or worse). Ibid. 68.
Inwagen uses some standard categories: greater good, greater evil, countervailing goods (i.e. goods that "outweigh" evils). He also talks about the possibility of particular evils that could have been "left out" without sacrificing any great good or permitting an even greater evil.
One problem with that analysis is his failure to define his terms. What makes something a greater good or greater evil? How is that identified?
Does he mean it in the collective sense of what is best overall? Is it like the common good (i.e. what's good for the most people)? Is it the most goods with the fewest evils?
This raises the question of how we count goods and evils. Are goods and evils discrete items? Can you put them in parallel columns to see that one possible world is better or worse than another?
Seems to me that in a fallen world, good and evil bleed into each other. For instance, there are virtuous parents of vicious kids and vicious parents of virtuous kids. So how do we separate that out in order to tabulate the respective goods and evils? Do they count as two distinct events or one seamless cause-and-effect event?
Let's take a more complex example. Suppose you have a teenager who's a good intramural athlete. When he goes to the shopping center, he always parks in front of the store, if there's an available slot, to save himself a few extra steps. That means he has no compunction about taking a disabled parking slot. He doesn't care about elderly customers with walkers or customers in wheelchairs who might actually need that slot. He's in a hurry, and he can't be bothered to walk a few extra yards from the parking lot to the store.
He has no empathy for the disabled. Indeed, as a natural athlete, he has a certain disdain for the disabled. He's proud of his body. Proud of his athletic prowess. He doesn't relate to the disabled. He's impatient with the disabled. They get in the way. They slow him down. He may even think they'd be better off euthanized.
Until a day when he's crossing the street. He is texting. The driver is texting. He doesn't see the approaching car. The driver doesn't see the pedestrian.
He wakes up in a hospital with spinal chord injury. No more intramural sports. He will be in a wheelchair for the rest of his life.
Of course, now he sees the world from the other side of the wheelchair. Now he resents able-bodied shoppers who take the disabled parking slot. He sees himself, when he was the same way.
His new existence is extremely frustrating. And he becomes socially isolated, because his buddies and girlfriend tune him out of their lives, now that he can't keep up with them. Having him tag along is inconvenient. They'd have to go at his pace. That's no fun.
But there's another side to this. He becomes the caring, considerate, observant person he never used to be. He becomes a good listener. He develops an empathy he never had before, because he is forced to identify with the weak and lonely. He hates it, but it makes him a better person.
How do we count that? In one sense, it's better to be able-bodied than disabled. His physical disability is a natural evil. Yet it becomes the source of moral good. A soul-making virtue. A fallen world is a blended world of good and evil. A world in which the boundaries of good and evil are blurry.
You can arrange possible worlds along a spectrum of good and evil. You can distinguish possible worlds at the extremes of good and evil, where a greater good or greater evil occupy the farther ends of the spectrum. But closer to the middle, it's harder to say what's better or worse overall, because the goods and evils bleed into one another in ways that aren't easily separable. There are centers of good and centers of evil, but the circumference is blended. Primary colors of good and evil inside secondary colors where good and evil mix.