Joe is baking cupcakes for Sally. He has an inculpable false belief that cyanide is a tasty nutritional supplement and so adds it to the cupcakes to improve the taste, indeed killing Sally. Sally was innocent.
Fred is baking cupcakes for Samantha. He has an inculpable false belief--perhaps acquired through brainwashing--that it is right to kill any people one likes for fun and so adds cyanide to the cupcakes to kill Samantha for fun, and indeed he kills her. Samantha was innocent.
Neither Joe nor Fred are culpable (though in practice it would take a lot of convincing to make us agree that their beliefs were inculpable). But I feel that there is a difference in the two cases. I am inclined to say that Fred acted wrongly, though not culpably, while I am less inclined to say the same thing about Joe. What's the relevant difference?
Well, one difference is that Joe acts because of an inculpably false empirical belief while Fred acts because of an inculpably false normative belief. But that difference doesn't seem the relevant one to me. We could imagine cases where being wrong about normative matters (say, about whether a particular person one is punishing has acted wrongly) leads to an error more like Joe's than Fred's.
So what's the difference? Well one difference that does seem relevant to me is this. Both Joe and Fred are killing innocent people. But Joe doesn't act under the description killing an innocent person while Fred does. Thus Fred acts under a description that entails the wrongness of the action (assuming that it's necessarily always wrong to kill an innocent) while Joe does not. I think this is getting close, but doesn't quite get at the difference. Suppose Joe does something that he knows to be is a killing if and only if some complex mathematical statement p is true, and Joe is inculpably sure that the statement is false, though it's actually necessarily true. It may well be that Joe is acting under the description killing an innocent person if and only if p and an action's falling under this description does entail the wrongness of the action.
Maybe the right tool for distinguishing the two cases is intention? Joe doesn't intentionally kill. Fred does. That's certainly a very relevant difference. But we can imagine a case like Joe's where there is intentional killing. Suppose James is a law enforcement officer with the inculpable false belief that Suzy is trying to kill innocent people. (Perhaps he's wondered on a movie set where Suzy is playing a mass shooter with great plausibility and superb special effects.) Then James intentionally kills Suzy, but his error seems much more like Joe's than like Fred's. Maybe we can, however, say that James is not intentionally killing an innocent, while Fred is. But that could be a misunderstanding of Fred's intentions as far as my description goes. The story can be elaborated so Fred is no more intending to kill an innocent than if I shake hands with you I am intending to shake hands with someone wearing a green shirt (assuming you're obviously wearing a green shirt). Your wearing a green shirt just doesn't enter into my intentions, and we can suppose that Fred gets no special pleasure out of the innocence of the person he kills, so that innocence doesn't enter into his intentions.
Nonetheless, perhaps we can say this: It is always wrong to intend to kill someone. It is not always wrong to intend to kill an aggressor. But when a person virtuously intends to kill an aggressor, maybe she doesn't automatically intend to kill this person. Rather, she intends to kill this aggressor. This person's being an aggressor suffuses her intentions. Thus James who kills Suzy the apparent aggressor doesn't have the intention to kill Suzy or to kill a person. He has the intention to kill Suzy the aggressor, an intention that he fails to fulfill. If that's right, then we can say that both Joe and James act under a morally upright intention: to flavor cupcakes an to kill an aggressor, respectively.
I am worried about this solution, though. It may require more to be packed into morally upright intentions than is psychologically realistic. After all, it's not right to kill an aggressor as such. It's only right to kill an aggressor who threatens significant harm and cannot be stopped in non-lethal ways and there are surely lots of other conditions (e.g., Aquinas thinks that only officers of the state have the right to intentionally kill--we can defend ourselves in unintentionally lethal ways, he allows, however). Should we pack all of all these conditions into James' intention? Maybe James can summarize mentally. He intends to rightly kill this aggressor. And rightly killing this aggressor is an intention that has the property that necessarily an action that fulfills it is right. However, the very same thing could be said about Fred's case. Given Fred's belief that it's right to kill for fun, Fred could be intending to rightly kill Samantha.
I wish I had a satisfactory resolution. Maybe we don't need the upright intention to entail rightness. Maybe all James needs is the intention to kill an aggressor, even though not all cases of killing an aggressor are right?
I really don't know. As I think about cases like this, I wonder how sharp the distinction between Joe and James, on the one hand, and Fred, on the other, really is. Maybe all we have is a vague distinction that Joe and James' errors do not constitute them as morally corrupt, while Fred's error does constitute him as morally corrupt (even if he is not culpable for this moral corruption). But that distinction doesn't cut quite the line we want. Take my mathematical case and change p into a moral proposition. Suppose Joe has the inculpable false belief that theft is right and intends that Sally die if and only if theft is wrong. Then Joe's root error does constitute him as morally corrupt, but he's still not like Fred. Nonetheless, even though the distinction between beliefs that make one morally corrupt and those that don't may not cut the exact line we want, maybe that's the only non-gerrymandered line to be cut here? I really want to say that Joe and James both did something that we wish they hadn't done, while Fred did something wrong, even though all three were non-culpable. But I don't know if I can support this distinction.