1. Ed would have lived if neither action occurred.
2. Either action was sufficient to cause Ed’s death.
3. Both actions, together, were still sufficient to cause Ed’s death.
C: Ed is dead as a result of their actions. Charge both with murder.

So we have individual and joint sufficiency, actus reus and mens rea, and a result that would not have occurred without the acts. This seems to be enough to condemn both Bob and George of murder.
Of course, it’s easy to confuse our intuitions by talking about cause and individual responsibility. But I think individual and joint sufficiency means we can assign responsibility to both parties, regardless of our intuitional confusions about individual causation.

I don’t think it matters if the canteen is usable or not. I think we are supposed to be imagining that canteen slowly leaks and Ed doesn’t discover it is empty until much later and he is in the desert, where the empty canteen is useless whether it has a hole or not. But for the sake of clarity, let’s imagine George empties it without damaging it.

“In this story, though, you’re guilty of attempted hungermongering.”

Precisely. I’m guilty of ATTEMPTED hungermongering because I tried to take away your food and failed. And George (like Bob) is only guilty of ATTEMPTED murder (via thirstmongering) because he tried to take away Ed’s viable drinking water and failed (again, because there was no viable drinking water).

What I think might be driving the intuition that George does cause Ed to die of thirst is the fact that Ed would not have died of thirst if he had drank the poison. So granted, George’s act of poking a hole in the canteen (or emptying it) is a necessary condition for Ed to die of thirst. But it still is not the cause. Again, to CAUSE Ed to die of thirst, George would have to deny Ed access to viable drinking water, and George simply failed to do that. There was no viable drinking water in Ed’s canteen. If Ed had unwittingly been carrying a bomb, removing the bomb would also be a necessary condition for Ed to die of thirst. But we would not (I don’t think) say that the person who removed the bomb from Ed’s backpack caused Ed to die of thirst.

This one feels like the gap; I think the prisoner’s correctly deduced a contradiction, but not a paradox. The judge is simply wrong to group Friday’s execution in with all the other days; Friday’s execution date is a special case because of its edge condition.

-Wm