The Unselfish Trolley Problem

By now the Trol­ley Prob­lem is well known amongst moral philoso­phers and LessWrong read­ers. In brief, there’s a trol­ley hurtling down the tracks. The das­tardly villain Snidely Whiplash has tied five peo­ple to the tracks. You have only sec­onds to act. You can save the five peo­ple by throw­ing a switch and trans­fer­ring the trol­ley to an­other track. How­ever the evil villain has tied a sixth per­son to the al­ter­nate track. Should you throw the switch?

When first pre­sented with this prob­lem, al­most ev­ery­one an­swers yes. Sacri­fice the one to save five. It’s not a very hard choice.

Now comes the hard ques­tion. There is no switch or al­ter­nate track. The trol­ley is still com­ing down the tracks, and there are still five peo­ple tied to it. You are in­stead stand­ing on a bridge over the tracks. Next to you is a fat man. If you push the man onto the tracks, the trol­ley car will hit him and de­rail, sav­ing the five peo­ple; but the fat man will die. Do you push him?

This is a re­ally hard prob­lem. Most peo­ple say no, they don’t push. But re­ally what is the differ­ence here? In both sce­nar­ios you are choos­ing to take one life in or­der to save five. It’s a net gain of four lives. Espe­cially if you call your­self a util­i­tar­ian, as many folks here do, how can you not push? If you do push, how will you feel about that choice af­ter­wards?

Try not to Kobayashi Maru this ques­tion, at least not yet. I know you can crit­i­cize the sce­nario and find it un­re­al­is­tic. For in­stance, you may say you won’t push be­cause the man might fight back, and you’d both fall but not till af­ter the trol­ley had passed so ev­ery­one dies. So imag­ine the fat man in a wheelchair, so he can be lightly rol­led off the bridge. And if you’re too so­cially con­strained to con­sider hurt­ing a hand­i­capped per­son, maybe the five peo­ple tied to the tracks are also in wheelchairs. If you think that be­ing pushed off a bridge is more ter­rify­ing than be­ing hit by a train, sup­pose the fat man is thor­oughly anes­thetized. Yes, this is an un­re­al­is­tic thought ex­per­i­ment; but please play along for now.

Have your an­swer? Good. Now comes the third, fi­nal, and hard­est ques­tion; es­pe­cially for any­body who said they’d push the fat man. There is still no switch or al­ter­nate track. The trol­ley is still com­ing down the tracks, and there are still five peo­ple tied to it. You are still stand­ing on a bridge over the tracks. But this time you’re alone and the only way to stop the train is by jump­ing in front of it your­self. Do you jump? If you said yes, you would push the fat man; but you won’t jump. Why?

Do you have a moral obli­ga­tion to jump in front of the train? If you have a moral obli­ga­tion to push some­one else, don’t you have a moral obli­ga­tion to sac­ri­fice your­self as well? or if you won’t sac­ri­fice your­self, how can you jus­tify sac­ri­fic­ing some­one else? Is it morally more right to push some­one else than jump your­self? I’d ar­gue the op­po­site...

Real­is­ti­cally you may not be able to bring your­self to jump. It’s not ex­actly a moral de­ci­sion. You’re just not that brave. You ac­cept that it’s right for you to jump, and ac­cept that you’re not that moral. Fine. Now imag­ine some­one is stand­ing next to you, a skinny ath­letic per­son who’s too small to stop the train them­selves but strong enough to push you over into the path of the trol­ley. Do you still think the cor­rect an­swer to the trol­ley prob­lem is to push?

If we take it se­ri­ously, this is a hard prob­lem. The best an­swer I know is Rawlsi­anism. You pick your an­swer in ig­no­rance of who you’ll be in the prob­lem. You don’t know whether you’re the pusher, the pushed, or one of the peo­ple tied to the tracks. In this case, the an­swer is easy: push! There’s a 67 chance you’ll sur­vive so the self­ish and util­i­tar­ian an­swers con­verge.

We can play other var­i­ants. For in­stance, sup­pose Snidely kid­naps you and says “To­mor­row I’m go­ing to flip a coin. Heads I’ll put you on the tracks with 4 other peo­ple (and put a differ­ent per­son on the bridge next to the pusher). Tails I’ll put you on the bridge next to a pusher.” Should the pusher push? Ac­tu­ally that’s an easy one be­cause you don’t know where you’ll end up so you might as well save the four ex­tra peo­ple in both sce­nar­ios. Your ex­pected value is the same and ev­ery­one else’s is in­creased by push­ing.

Now imag­ine Snidely says in­stead he’ll roll a die. If it comes up 1-5, he puts six peo­ple in­clud­ing you on the track. If it comes up 6, he lets you go and puts the other five peo­ple on the track. How­ever if you agree to be tied to the track with­out a roll, with­out even a chance of es­cape, he’ll let the other five peo­ple go. What now? Sup­pose he rolls two dice and they both have to come up 6 for you to go free; but he’ll still let ev­ery­one else go if you agree. Will you save the other five peo­ple at the cost of a 136 chance of sav­ing your own life? How about three dice? four? How many dice must Snidely roll be­fore you think the chance of sav­ing your own life is out­weighed by the cer­tainty of sav­ing five oth­ers?

Do you have your an­swers? Are you pre­pared to defend them? Good. Com­ment away, and you can even Kobayashi Maru the sce­nario or crit­i­cize the ex­ces­sively con­trived hy­po­thet­i­cals I’ve posed here. But be fore­warned, in part 2 I’m go­ing to show you an ac­tual, non-hy­po­thet­i­cal sce­nario where this prob­lem be­comes very real; in­deed a situ­a­tion I know many LessWrong read­ers are fac­ing right now; and yes, it’s a mat­ter of life and death.


Up­date: It now oc­curs to me that the sce­nario can be tight­ened up con­sid­er­ably. For­get the bridge and the fat man. They’re ir­rele­vant de­tails. Case 1 is as be­fore. 5 peo­ple on one track, 1 on an­other. Pull the switch to save the 5 and kill the 1. Still not a hard prob­lem.

Case 2: same as be­fore, ex­cept this time you are stand­ing next to the one per­son tied to the track who will be hit by the trol­ley if you throw the switch. And they are con­scious, can talk to you, and see what you’re do­ing. No one else will know what you did. Does this change your an­swer, and if so why?

Case 3: same as be­fore, ex­cept this time you are the one per­son tied to the track who will be hit by the trol­ley if you throw the switch.

Folks here are be­ing re­fresh­ingly hon­est. I don’t think any­one has yet said they would throw the switch in case 3, and most of us (my­self in­cluded) are sim­ply ad­mit­ting we’re not that brave/​al­tru­is­tic/​suici­dal (as­sum­ing the five peo­ple on the other track are not our friends or fam­ily). So let’s make it a lit­tle eas­ier. Sup­pose in case 3 some­one else, not you, is tied to the track but can reach the switch. What now?

Up­date 2: Case 4: As in case 3, you are tied to the track, five other un­re­lated peo­ple are tied to the op­po­site track, and you have ac­cess to a switch that will cause the trol­ley to change tracks. How­ever now the trol­ley is ini­tially aimed at you. The five peo­ple on the other track are safe un­less you throw the switch. Is there a differ­ence be­tween throw­ing the switch in this case, and not throw­ing the switch in Case 3?

This case also raises the in­ter­est­ing ques­tion of le­gal­ity. If there are any lawyers in the room, do you think a per­son who throws the switch in case 4--that is, saves them­selves at the cost of five other lives—could be con­victed of a crime? (Of course, the an­swer to this one may vary with ju­ris­dic­tion.) Are there any ac­tual prece­dents of cases like this?