Deontology, as standardly formulated, holds that there are some acts that you shouldn’t take even for the greater good and indeed even to prevent more of such acts. For example, you shouldn’t kill to prevent two killings. But strangely, the deontologist is committed to thinking that, for many of these acts, you shouldn’t try to prevent others from taking them. Or so I’ll argue.

The argument against deontology is as follows (I’ll use a paradigm case of killing one to prevent two killings here).

If deontology is true, then you shouldn’t kill one person to prevent two killings.
If you shouldn’t kill one person to prevent two killings, then, all else equal, you should prevent another person from killing one person to prevent two killings.
All else equal, you should not prevent another person from killing one person to prevent two killings.

Therefore, deontology is false. I’ll defend each of the premises.

1

If deontology is true, then you shouldn’t kill one person to prevent two killings.

This is true by definition.

2

If you shouldn’t kill one person to prevent two killings, then, all else equal, you should prevent another person from killing one person to prevent two killings.

The idea here is pretty simple. It seems really obvious that you should prevent people from doing wrong things if you can at no personal cost. In fact, as this paper. which started the entire idea of this worry for deontology in my mind notes, this produces a strange result when it comes to deterrence. Presumably, if we think that killing one to save five is wrong, we’ll think that it’s a good thing that laws against murder prevent that. But if we think that third parties have no reason to prevent killing one to save five, then deterrence is not a reason to ban deontic rights violations with good outcomes.

If you have no reason to prevent organ harvesting, then it isn’t wrong. One should prevent wrongdoing, if all else is held equal. .

3

All else equal, you should not prevent another person from killing one person to prevent two killings.

This argument has a supporting argument.

Deontology either is or is not true.
If deontology is not true, you should not prevent another person from killing one person to prevent two killings.
If deontology is true, you should not prevent another person from killing one person to prevent two killings.

Therefore, you should not prevent another person from killing one person to prevent two killings.

1 and 2 are trivial—I’m using deontology to mean merely that there are constraints, so if there aren’t, then you should kill one to prevent two killings. The only point in dispute is 3.

There are four reasons to accept three. The first one is defended in detail by the original paper—deontology just has no principled explanation of why you should prevent deontological wrongs. After all, third parties aren’t responsible for deontological wrongs they don’t prevent, but they do have some reason to make things better. Deontologists agree that you should promote the good, all else equal. Thus, they should recognize that you have some reason not to prevent a killing to prevent two killings—a consequentialist one—and no other deontological reasons to prevent it. Thus, all things considered, there’s no account of why one ought to prevent it.

Second, Richard’s paradox decisively shows that even deontologists should hope that you kill one to prevent multiple killings. But if you ought to want something to happen, you shouldn’t prevent it from happening.

Third, there’s a clear deontic reason not to prevent one killing to prevent multiple killings. After all, this is causing two murders to prevent one. It is clearly wrong—on both deontology and other theories—to cause two murders to prevent one.

Four, let’s imagine that someone else commits one killing to prevent you from killing two. It seems obviously wrong, on deontology, to take some action that will result in you directly killing two to prevent someone else from killing one.

Conclusion

Thus, we have one more explanation of why deontology is false. It holds that you shouldn’t prevent others from doing the wrong thing, bizarrely.

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