Trolley Problems

by Brian on August 30, 2003

A staple of intro philosophy courses is the ethics of runaway trolleys. There’s probably an interesting sociological study as to why this is so, but rather than delve into that I thought I’d share a new-sounding version of the trolley problem due to Carolina Sartorio posted on Philosophy from the (617).

For those who’ve missed this line of study before, the puzzles arise from reflecting on cases like the following.

bq. Basic Trolley Case: There is a run away trolley car careening down some railway tracks towards two tunnels. If it stays on the track it is on, it will kill five people working in the eastern tunnel. If you pull a switch it will move onto a side track, go through the western tunnel and kill the person working in it. Assume you can’t do anything to stop the car or change its path except pull this switch. You pull the switch, saving the five and leading to the one’s death.

bq. Fatman: Same runaway car, but without the switch. This time, you’re standing on a cliff looking over the track the car is about to careen down. If unchecked it will kill the five people in the tunnel. Fortunately, there is a very fat man standing beside you – fat enough that if somehow he were to fall onto the track his sheer mass would stop the trolley. You give him a little shove, he falls off the cliff onto the train tracks is killed by the trolley (if not the fall) and the five are saved.

A significant number of people think your action in the first case is permissible, perhaps even mandatory, but the action in the second case is impermissible. Providing a reason for the different attitudes towards the two actions is not entirely trivial, which I guess is one of the reasons these cases are staples of intro philosophy courses.

Here’s Carolina’s case.

bq. Fatman*: There are five people tied up to a track. One of them is a fat man, and somehow I can shove him into the path of the train (although I can’t save him!) to stop the train before it kills the other four.

There’s two puzzles here. The first, in which Carolina is interested, is whether the action is permissible in this case. The second, which seems more fun to me, is whether we can tell anything like a plausible story in which the facts are as Carolina stipulates. I’m moderately dubious that this can be done, but I should never underestimate the powers of storytellers.

I wonder if the intuitions about the cases will differ depending on just how the details are set out. Just for fun, here’s a variant that I think is like the Basic Trolley Case.

bq. Evil Demon: An evil demon has set up a run away steam engine to travel through five tunnels, killing the people tied to the tracks in each tunnel. You can’t stop the train (it’s got a really powerful engine) but you can change the order in which the train goes through various tunnels. You notice that the man tied to the tracks in tunnel #5 (i.e. the tunnel the train is scheduled to go through fifth) is really fat. It looks probable the train will derail when it hits him. (It’s a pretty resilient train, so it can run over the supermodels in the other four tunnels without being derailed, but it can’t handle the fat man. Probably.) So you reroute the train to go through his tunnel first, it hits him, kills him and is derailed, saving the four.

Is this action permissible? Is it mandatory? Is it a sign of completely awful character that one even thinks about these puzzles? Of worse character to write about them? I don’t know – I just do time travel.



Elina 08.30.03 at 9:14 am

I think the explanation for the different intuitions on these trolley cases is quite simple but has nothing to do with morality (which is bunk in my opinion). Intuitions need only to be emotionally understandable whereas moral propositions need to be rationally consistent and that’s why we even bother with these stories.

I think the answer is that of course we feel that it’s better to kill one person than five, given that our emotional hand in the death will feel the same either way. However, when we think about actively sacrificing the fat man, pushing him, looking into the horrified whites of his eyes, we just can’t do it.

Not very philosophical but it makes a certain amount of sense.


Chris 08.30.03 at 9:27 am

Not about the trolley problem at all, but does fact that Carolina Sartorio and Juan Comesana (from Philosophy from the (617)) and Harry Brighouse (from CT) are all at Madison, Wisconsin make the Philosophy Dept there the most blog-intensive one in the world?


Jack 08.30.03 at 10:14 am

Isn’t this like cruelty to animals? Pulling the wings off flies is not obviously bad in itself but enyone doing so might be more likely to break an welcome taboo in a more important case. (Ithink it possible to attribute the good aspects of this argument to someone more eminent than myself but I won’t risk embarassing myself by guessing)

It is quite important to me to know that those around me are unlikely to consider violence against me and I can function better as a result.

As an example, suppose I am walking along a cliff when my rational philospher friend observes a trolley on the tracks below. The trolley operator looks very healthy while I, he knows, am going to have a minor operation which involves a small but measurable risk of death because of the general anaesthetic.

The philosopher identifies two courses of action to save the peole in the tunnel — push me off the cliff to block the trolley saving everyone but me or push a boulder off the cliff stopping the trolley but killing its operator.

I hope he would go for the operator but the expected number of people alive by the end of the week is less if he does.


Lawrence Solum 08.30.03 at 4:08 pm

There is a nice wikipedia entry on the Trolley Problem, with links & references:


JW 08.30.03 at 11:13 pm

I thought that there was already an extant trolley case like the one you describe, except that the setup involves a round track. 5 people are tied up on the track, exactly one of whom is large enough to stop the train if it hits him. A train is heading into the circle, and after it enters it will traverse the track to hit the fat guy last. You can throw a switch so that it will go around the track the other way — hitting the fat guy first, and saving the other 4. Ought/can you throw the switch?

Isn’t this already in the literature somewhere? (Damnit, Jim, I’m an epistemologist, not an ethicist!)


Neel Krishnaswami 08.30.03 at 11:21 pm

Do moral propositions even need to be logically consistent with respect to classical logic?

I mean, it’s a) obvious that people don’t reason according to classical logic, and b) they are correct not to do so. In classical logic contradictions let you infer any proposition, and in real life we have to reconcile lots and lots of inconsistent data. So maybe people reason using a relevant or paraconsistent logic that can tolerate a certain amount of uncertainty: moral reasoning can’t say anything useful in the case of killing the fat man, because it induces a contradiction, but it can still tell you that cuddling a puppy is better than sticking it in the blender and pureeing it.


Carolina 08.31.03 at 2:39 am

JW is right. He is describing Judy Thomson’s Loop case. Thomson argues (in “The Trolley Problem”, reprinted in _Rights, Restitution and Risks_) that it is permissible to flip the switch in Loop. But I think it’s different from Fatman*.


Kieran Healy 08.31.03 at 3:24 am

Don’t forget to consider what to do when, among other things, a brain in a vat is driving the trolley on twin earth. What’s your intuition on this? (You do have one, don’t you?)


Jurjen Smies 08.31.03 at 11:53 am

If, in the case of the Loop Problem, the fat man will be hit (and therefore be killed) irrespective of the trolley’s route, the question is rather moot, isn’t it? Throw the switch and the fat man dies; don’t throw the switch and the fat man also dies, but five (or four, whichever) other people die with him. Where’s the dilemma?

Unless we assume that if the trolley runs over the other five people first, there is some insanely steep gradient which will stop the trolley before it reaches the fat man, in which case I recommend shooting the railway engineer who designed the track (providing the ghost of Isambard Kingdom Brunel hasn’t throttled him already) before he does more damage.


OmerosPeanut 09.01.03 at 9:07 pm

If markets trumped moral/ethical judgements:

Now suppose that in the basic trolley problem you are a personal injury lawyer. Do you let the trolley kill the five people in order to gain five clients (the innocents’ respective families) rather than a mere one were you to switch the trolley to the other track?

My apologies.

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