Over at Philosophy etc, Bradley Gabbard argues that a widespread intuition about the trolley problem can justify compulsory aid to the global poor. Here is the trolley problem:

• A runaway trolley is on course to kill five innocent people. I can switch the trolley to another track, saving the five but killing one (let’s call this guy Bob.)

According to Gabbard, about 90% of us have the intuition that it is morally permissible to divert the trolley in this case, killing Bob.  From that premise, it’s off to the races. If I can kill Bob to save five then Bob could similarly kill me. If Bob could kill me then Bob could also permissibly destroy my stuff. If Bob can destroy my stuff he can take it and redistribute it. If Bob can take and redistribute my stuff to save the five on the track then he can do it to save five people who would otherwise die in poverty. Therefore, compulsory aid to the global poor is permissible.

Hold on. The fact that 90% of us supposedly have this intuition in trolley cases doesn’t make it the right call. In Judith Thomson’s famous Fat Man case (where Bob is a fat man you must push in front of the trolley to save the five) our intuitions go the other way. And of course, almost no one believes you can run around murdering people to redistribute their organs to five sick patients, thus killing one to save five. Even in the trolley case, I doubt that so many of us would divert the trolley to kill an innocent person if we vividly imagined ourselves in that situation. I should hope that would be extremely psychologically traumatic to anyone who did turn the trolley to kill one. It’s not an easy premise to swallow.

One of my favorite articles on this topic is Thomson’s Turning the Trolley. There, she argues that we are not entitled to turn the trolley, push the fat man, or kill for organs—they’re all wrong. While I cannot do her brilliant argument justice in this post, here is the central case. In Bystander’s Three Options, I can:

• (i)  do nothing, letting five die, or
• (ii)  turn the switch to the right, killing Bob, or
• (iii) turn the switch to the left, killing myself.

Thomson writes that in this case (ii) would clearly be wrong. Say I think it would be a good deed to turn the switch. Still, I am surely not entitled to impose the cost of my good deed on Bob when I could bear the cost myself. By analogy, Thomson writes,

Compare the following possibility. I am asked for a donation to Oxfam. I want to send them some money. I am able to send money of my own, but I don’t feel like it. So I steal some from someone else and send that money to Oxfam. That is pretty bad. But if the bystander proceeds to turn the trolley onto the one on the right-hand track in Bystander’s Three Options, then what he does is markedly worse, because the cost in Bystander’s Three Options isn’t money, it is life.

So when we face three options, (ii) is wrong. And while altruistic suicide (iii) is permissible, morality cannot require me to kill myself to save the five, even if we all agreed that it would be a good deed. Even if altruistic suicide is the only permissible way to save the five, it isn’t required.

In a fascinating aside, Thomson also suggests that choosing (iii), while permissible, may be kinda messed up anyhow:

I stop to mention my impression that altruism that rises to this level is not morally attractive. Quite to the contrary. A willingness to give up one’s life simply on learning that five others will live if and only if one dies is a sign of a serious moral defect in a person.

Hardcore libertarian commenters (you know who you are) take note. Even if you disagree, it still wouldn’t follow from the fact that you would be willing to die to save five that you can permissibly kill someone else (Bob, the Fat Man, or the unwilling organ donor) to save five.

Thomson’s argument concludes with another genius move. Say I am examining the switch, and I then find that (iii) is actually not an option—altruistic suicide is off the table. Now we are back to the original Trolley problem but the impermissibility of (ii) remains. It is still impermissible for me to turn the trolley and kill Bob, making him pay the cost of my ‘good deed.’

So let’s take stock. If I am not required to kill myself to save the five (iii) then it is permissible to do nothing (i).  Killing Bob (ii) is not permissible, regardless of whether (iii) is an option. So in the original trolley case we ought to do nothing (i). Point is, don’t kill Bob.

I love Thomson’s argument, and I think it’s a great illustration of how weighty negative duties are. Still, I’m not sure that the trolley problem is, as she suggests, a non-problem after all. On this case I agree with Thomson’s judgment, but my intuitions remain frustratingly unclear about the weight of negative and positive duties more generally. Yes, negative duties are especially weighty. But this is not to say that they have absolute weight over positive duties or that positive duties don’t exist.

What if there were 500 people on the track and Bob’s life on the other one? Even then I am hesitant to say we can kill Bob. This case just looks too close to those ticking bomb cases, or the assassin case, and I think Jeremy Waldron’s response to the ticking bomb argument for torture is compelling:

Law and morality and religion requires that in no circumstances is torture to be used. The law is unambiguous, it’s a total prohibition. And for some of us, our morality dictates the same. We [should] take responsibility for the consequences of the bomb’s explosion, for the consequences of our morality.

As with torture, the same goes for killing. Still, if the numbers get high enough—I just don’t know what to do with those cases.

On the other hand, there are troubling counter examples to thinking that all negative duties have absolute priority. While I couldn’t permissibly kill Bob, could I injure him or destroy his property? Say I cannot bear the costs myself. It seems like I could divert the track in a way that ran over Bob’s toe, or his iPod, in order to save the five. Probably I should too. After all, if there were nothing on the other track then it would be really awful (and intuitively wrong) if I didn’t turn the trolley. How do we make sense of this? At what point does it become wrong to make Bob pay the price of my ‘good deed’?