Frances Kamm uses her principle of triple effect to resolve the loop version of the trolley problem. On the loop version, as usual, the main track branches into are two tracks, track A with five people and track B with one person, and the trolley is heading for track A. But now the two tracks join via a loop, so if there were no one on either track, a trolley that goes on track A will come back on track B and vice versa. If we had five people on track A and no one on track B, and we redirected the trolley to track B, it would go on track B, loop around, and fatally hit the people on track A anyway. But the one person actually on track B is big enough that if the trolley goes on track B, it will be stopped by the impact and the five people will be saved.
The problem with redirecting to track B on the loop version of the trolley problem is that it seems that a part of your intention is that the trolley should hit the person on track B, since it is that impact which stops the trolley from hitting the five people on track A. And so you are intending harm to the person on track B.
In her Intricate Ethics book, Kamm gives basically this story about redirecting the trolley in the loop case:
Initial Intention: Redirect trolley to track A to prevent the danger of five people being hit from the front.
Initial Defeater: The five people come to be in danger of being hit from the back by the trolley.
Defeater to Initial Defeater: The one person on track B blocks the trolley and prevents the dangers of being hit from the back.
The important point here is that the defeater to the defeater is not intended—it is just a defeater to a defeater. Thus there is no intention to block the trolley via the one person on track B, and hence that person’s being hit is not a case of their intentionally being used as a means to saving lives.
But this defeater-defeater story is mistaken as it stands. For given the presence of the person on track B, there is no danger of the five people being hit from the back. Thus, there is no initial defeater here.
Now, if you don’t know about the one person on track B, you would have a defeater to the redirection, namely the defeater that there is danger of being hit from the back. But learning about the person on track B would not provide a defeater to that defeater—it would simply remove the defeater by showing that the danger doesn’t exist.
That the story doesn’t have a defeater-defeater structure does not mean that one is intending the one person to be hit. Kamm might still be right in thinking there is no intention to block the trolley via the one person on track B. But I am dubious of Kamm’s story now, because I am dubious that the danger of being hit from the front yields a worthy initial intention. For there is nothing particularly bad about being hit from the front. It is only the danger of being hit simpliciter that seems worth preventing.
It is interesting to me to note that even if Kamm’s story doesn’t have defeater-defeater form, the main place where I want to use her triple effect account seems to still have defeater-defeater form. That place is the felix culpa, where God allows Adam and Eve to exercise their free will, even though he knows that this would or might well (depending on details about theories of foreknowledge and middle knowledge) result in their sinning, and God’s reasoning involves the great goods of salvation history that come from Adam and Eve’s sin.
Initial Intention: Allow Adam and Eve to exercise their free will.
Initial Defeater: They will or might well sin.
Defeater to Initial Defeater: Great goods will come about.
Here the initial defeater is not mistaken as in the looping trolley case—the sin or its possibility is really real. Moreover, while it’s not an initially worthy intention to prevent people from being hit from the front, unless they aren’t going to be hit from behind (or some other direction) either, it is an initially worthy intention to allow Adam and Eve to exercise their free will, even if no further goods come about, because free will is intrinsically good.
Thus we can criticize Kamm’s own use of triple effect while yet preserving what I think is a really important theological application.
