## Friday, November 13, 2020

### Reducing Triple Effect to Double Effect

Kamm’s Principle of Triple Effect (PTE) says something like this:

• Sometimes it is permissible to perform an act ϕ that has a good intended effect G1 and a foreseen evil effect E where E causally leads to a further good effect G2 that is not intended but is a part of one’s reasons for performing ϕ (e.g., as a defeater for the defeater provided by E).

Here is Kamm’s illustration by a case that does not have much moral significance: you throw a party in order to have a good time (G1); you foresee this will result in a mess (E); but you expect the partygoers will help you clean up (G2). You don’t throw the party in order that they help you clean up, and you don’t intend their help, but your expectation of their help is a part of your reasons for throwing the party (e.g., it defeats the mess defeater).

It looks now like PTE is essentially just the Principle of Double Effect (PDE) with a particular way of understanding the proportionality condition. Specifically, PTE is PDE with the understanding that foreseen goods that are causally downstream of foreseen evils can be legitimately used as part of the proportionality calculation.

One can, of course, have a hard-line PDE that forbids foreseen goods causally downstream of foreseen evils to be legitimately used as part of the proportionality calculation. But that hard-line PDE would be mistaken.

Suppose Alice has her leg trapped under a tree, and if you do not move the tree immediately, the leg will have to be amputated. Additionally, there is a hungry grizzly near Bob and Carl, who are unable to escape and you cannot help either of them. The bear is just hungry enough to eat one of Bob and Carl. If it does so, then because of eating that one, it won’t eat the other. The bear is heading for Bob. If you move the tree to help Alice, the bear will look in your direction, and will notice Carl while doing so, and will eat Carl instead of Bob. All three people are strangers to you.

It is reasonable to say that the fact that your rescuing Alice switches whom the bear eats does not remove your good moral reason to rescue Alice. However, if we have the hard-line PDE, then we have a problem. Your rescuing Alice leads to a good effect, Alice’s leg being saved, and an evil, Carl being eaten. As far as this goes, we don’t have proportionality: we should not save a stranger’s leg at the expense of another stranger’s life. So the hard-line PDE forbids the action. But the PDE with the softer way of understanding proportionality gives the correct answer: once we take into account the fact that the bear’s eating Carl saves Bob, proportionality is restored, and you can save Alice’s leg.

At the same time, I think it is important that the good G1 that you intend not be trivial in comparison to the evil E. If instead of its being a matter of rescuing Alice’s leg, it were a matter of picking up a penny, you shouldn’t do that (for more argument in that direction, see here).

So, if I am right, the proportionality evaluation in PDE has the following features:

• we allow unintended goods that are causally downstream of unintended evils to count for proportionality, but

• the triviality of the intended goods when compared to the unintended evils undercuts proportionality.

In other words, while the intended goods need not be sufficient on their own to make for proportionality, and unintended downstream goods may need to be taken into account for proportionality, nonetheless the intended goods must make a significant contribution towards proportionality.

Harrison Lee said...

Here's a thought: You don’t move the limb because *Bob* will be saved but rather because *one of them*—Bob or Carl—will be saved either way. But is Carl’s death the means by which one of them are saved? It seems not, precisely because if he hadn’t been eaten, Bob would have, and so he, Carl, would have been saved. It seems like what guarantees the desired result, that one of them will be saved, is the size of the bear’s stomach, which is not impacted by the movement of the tree. So the good effect is not downstream of the evil effect.

Alexander R Pruss said...

I think the case is like the looping trolley, so let's think what your comment may say about the looping trolley.

On the looping trolley, the trolley is heading to five people on the left, and on the right track there is one person. Behind the people the tracks are joined up, so that if the five people weren't there, the trolley would loop around and hit the person on the right, and if you redirect to the right then if the one weren't there, the trolley would loop around and hit the five people.

Now imagine this variant of the looping trolley. On the left is Bob and on the right is Carl. Additionally, in front of Bob, Alice has her leg out. A leg is not enough to stop the trolley. So if nothing is done, the trolley will run over Alice's leg and kill Bob, and stop. If you redirect, it will kill Carl, and stop.

Redirecting the trolley is like moving the log: it has two effects--it saves Alice's leg and redirects the lethal danger from Bob to Carl. Just as the bear has a limited capacity stomach and can only eat one, the trolley has a limited kinetic energy and can only kill one person.

So I think whatever you say about the bear case should go through for the looping trolley variant. "You don’t redirect because *Bob* will be saved but rather because *one of them*—Bob or Carl—will be saved either way. But is Carl’s death the means by which one of them are saved? It seems not, precisely because if he hadn’t been eaten, Bob would have, and so he, Carl, would have been saved. It seems like what guarantees the desired result, that one of them will be saved, is the trolley's kinetic energy, which is not impacted by the rediretion. So the good effect is not downstream of the evil effect."

Label things in the classic looping trolley case like this: on the left there are Bob and four nameless people, D, E, F and G. On the right there is Carl. We have a similar structure. The only difference is that Alice's leg is replaced by D, E, F and G. If it's OK to redirect to save Alice's leg, it's OK to save D, E, F and G. And we can just take it that it's inevitable that one of Bob and Carl will be saved. It's not one's intention to save Bob or Carl, since that's inevitable, but it is one's intention to save D, E, F and G. So, does your clever response solve the classic looping trolley case, too?