Trolley Problems1
You've heard this one before:
TROLLEY
A runaway trolley is coming down the track. It is headed towards five
people2 who cannot get out of its way. A Passerby realizes that he can
save the five by throwing a switch and diverting the trolley down a siding,
but he also realizes that if he does so, the trolley will kill a Lone Man
standing on the siding.
Should you divert the trolley? Lots of folks say, "Yes!" Whether or not they are right is
an interesting problem, but it is not what philosophers call "The Trolley Problem." That
problem involves a different case:
FAT MAN
A runaway trolley is coming down the track. It is headed towards five
people who cannot get out of its way. A passerby realizes that if he
pushes a nearby fat man onto the tracks, his bulk will stop the trolley
1
First published April 30,2011 on www.tomkow.com.
2
Ignore the dog.
2
before it hits the five, though the fat man himself will be killed.
Most people, including those who think it is okay to turn in TROLLEY, think that it is not
okay to push the FAT MAN. "The Trolley Problem" is how to reconcile these two
answers. In both cases, it seems you can do something that will save five people but
only by killing one. How can anyone think it okay to turn in TROLLEY but wrong to push
the FAT MAN? What difference is there between the two stories that can possibly make
a moral difference?
In the almost forty years since Judith Jarvis Thomson first posed the problem in this
form, there have many attempts to solve it, but none is generally accepted as
successful. Indeed a general consensus seems to have developed that the "folk
intuitions" (as philosophers call them) about the difference between these cases are
simply irrational.
Thus a Utilitarian like Peter Unger can argue3 that, since there is no difference, it must
Unger, P. K. (2011). Living high and letting die: Our illusion of innocence. New York, NY:
Oxford Univ. Press.
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be morally okay to go around doing things like pushing fat men under trolleys so long as
it promotes the general happiness.
Meanwhile, Judith Jarvis Thomson concludes4 that, since there is no difference
between the cases, it must be wrong to turn in TROLLEY and so FAT MAN represents
a reductio ad absurdum of Utilitarianism.
Both sides explain away "folk intuitions" that the cases are somehow different as a
psychological aberration. Folks feel better about killing other folks in
TROLLEY-- this theory goes-- because they are more comfortable with
throwing a remote switch in TROLLEY than they are with the up close
shoving that FAT MAN requires. There are even psychological
"experiments" and (God help us) neural imaging studies that are
supposed to explain (away) these folksy confusions.5
In a conflict between folk intuitions and philosophical theory, I'll bet on the folk every
time. I'm not going to take a position here on whether or not it is permissible to turn in
TROLLEY or push the FAT MAN. My goal instead is to show that, as described, there
are subtle but important differences between the FAT MAN and TROLLEY cases;
differences that can make a moral difference in other circumstances, but differences
that have, hitherto, gone overlooked by philosophers.
We begin with some different thought experiments.
SACRIFICING OTHERS
A runaway trolley is coming down the track. It is headed towards a Lone
Man on the tracks who cannot get out of the way. However, that man is
standing by a switch which, if thrown, will divert the trolley down a siding.
In that case, the man will be safe, but he can also see that, in that case,
five people standing on the siding will be killed.
Thomson, J. J. (2008). Turning the Trolley. Philosophy & Public Affairs,36(4), 359-374.
doi:10.1111/j.1088-4963.2008.00144.x,
4
Cf. Tomkow, Allowing Experimental Philosophy. (n.d.).
https://tomkow.typepad.com/tomkowcom/2008/05/oh-agent-starli.html and Jerry Fodor
https://www.lrb.co.uk/v21/n19/jerry-fodor/diary for whinging about such boondoggles.
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4
Is it morally permissible for the man to throw the switch? If it is permissible, what of this:
SHIELDING ONESELF
A man sees that someone is about to shoot him. To protect himself, he
grabs an innocent bystander and uses her as a shield.
SHIELDING ONESELF
Now there is a line of thought that says that when one's life is in danger, anything goes.
The philosopher Hobbes seems to have held something like this position. But this
seems to me to throw morality out the window when it may be most required. It seems
to me that SHIELDING ONESELF and SACRIFICING OTHERS are clearly
impermissible and in what follows I'm going to assume you agree with me.
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Now consider.
SELF DEFENSE
A runaway trolley is coming down the track. Luckily there is no one in its
path. A passerby, Burns, sees this but he also notices that Homer,
someone he hates, is standing on a siding. Burns realizes that if he throws
a nearby switch, the trolley will be diverted down the siding killing Homer.
Homer can see all this too, and when he sees Burns moving towards the
switch, he correctly guesses his intent. Homer cannot get out of the way,
but he is not defenseless: he has a gun. He draws it and shouts "Stop, or
I'll shoot!". But Burns ignores him and keeps moving the switch.
SELF-DEFENSE
Assuming all these facts, I expect you to agree with me that it would be morally
permissible for Homer to pull the trigger. It seems an ordinary case of self-defense
albeit against an unusual attack.
Now for the interesting case:
SELF DEFENSE WITH COLLATERAL DAMAGE
A runaway trolley is coming down the track. It is headed towards five
people who cannot get out of its way. A passerby, Burns, sees this and
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realizes that he can save the five6 by throwing a switch and diverting the
trolley down a siding. Burns also realizes that if he does so, the trolley will
kill Homer, whom Burns hates. Homer can see all this too, and when he
sees Burns moving towards the switch, he correctly guesses his intent.
Homer cannot get out of the way, but he is not defenseless. He has a
gun…
SELF-DEFENSE WITH COLLATERAL DAMAGE
The only external difference between this case and SELF DEFENSE is the presence of
the people on the track, but I have also subtracted any reference to Burns' motive. Feel
free to imagine that Burns is primarily motivated by a desire to save the five, or primarily
by a desire to kill Homer, or by the combination of the two, but be prepared to say why
that makes a difference to the central question.
The central question being: is it permissible for Homer to use his gun to stop Burns?
I do not think that it is. Burns is going to divert the trolley and prevent the death of five
people. If Homer or anyone else stops Burns, they will be causing the death of five
people and preventing the death of only one. Of course, Homer's life is at risk, but we
6
I said ignore the dog.
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agreed when we considered the SACRIFICING OTHERS case that it was not
permissible for him to save his own life by doing something that would cause the death
of people who were no threat to him. That seems to apply in this case too, indeed more
so because now he will be harming Burns in addition to causing the death of the five.
Though I think that Homer would still be responsible for the death of the five if Burns
were stopped by Homer's yelling "Stop." Nor it doesn't seem to me relevant to the case
what Burn's motives happen to be.
If that is correct, then we have discovered something. People who say that it is wrong to
turn in TROLLEY sometimes argue that this is so because killing the man on the siding
infringes his rights. But we seem to have just discovered that the man on the siding
does not, in this circumstance, have all the rights that people ordinarily have. He doesn't
have a right to self-defense. He lacks that right—at least against Burns-- because in this
circumstance he can defend himself only by sacrificing others. And if Homer lacks the
right to self-defense here, so does the Lone Man in the original TROLLEY case. As
described, he didn't have a gun, but it doesn't matter: even if he did, he would not have
had the right to use it save himself.
Now, what about the Fat Man?
THE FAT MAN DEFENDS HIMSELF
A runaway trolley is coming down the track. It is headed towards five
people who cannot get out of its way. A passerby, Flanders, realizes that if
he pushes a nearby a fat man onto the tracks, his bulk will stop the trolley
before it hits the five, though the Fat Man himself will be killed. Flanders
decides to push the Fat Man. The Fat Man sees all this, but he is not
inclined to sacrifice himself to save the five, and when he sees Flanders
moving to push him onto the track he draws his gun and threatens "Stop,
or I'll shoot!". Flanders keeps coming...
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THE FAT MAN DEFENDS HIMSELF
Is it morally permissible for the Fat Man to shoot? All the arguments that applied in the
case of SELF-DEFENSE WITH COLLATERAL DAMAGE seem to apply here as well.
Flanders is going to do something that will keep five people from being killed. If the Fat
Man or anyone else stops him, they will be causing the death of those five people and
saving the life of only one. The Fat Man could claim he was acting in in self-defense but
isn't defending himself in this case as bad as it is in SACRIFICING OTHERS?
Maybe, but there are differences: they have to do with the different alternatives
available to Homer and the Fat Man.
Let us pause to remember that when we are deciding whether any action is permissible,
it is always relevant to ask what alternative actions are available. We all agree that it is
morally impermissible to kill. But in a case in which one's only alternative to killing one
person is to kill many people, most of us think that it is morally permissible if not
mandatory to kill the one rather than kill the many.
Now the TROLLEY case is interesting because the passerby's alternatives are not
whether to kill one or five but whether or not it is permissible to kill one rather than allow
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five to die. Some people think that allowing people to die is just as bad as killing them.
But this is a minority view. Most people think that harming people is morally worse than
allowing them to come to harm; TROLLEY tests that opinion.
The difference between allowing harm and causing it is especially vivid when preventing
harm to others involves incurring harm ourselves. When the Fat Man stares at the
speeding trolley, his choice is whether to allow five strangers to die or to prevent their
death by sacrificing himself. No one (at least, none of us folks) thinks this kind of
sacrifice is morally required of him, and none of us thinks that his refraining is equivalent
to his killing five people. If the Fat Man jumped on his own, he would be a hero precisely
because he would have been acting above and beyond the demands of morality.
But the situation is different in the case where THE FAT MAN DEFENDS HIMSELF. If
the Fat Man allows himself to be pushed, he will be sacrificing himself to save five. But if
he resists he will be causing their death by preventing their rescue. Notice that this is
not the choice that Homer faces in SELF DEFENSE WITH COLLATERAL DAMAGE.
Homer's choice was between causing the death of the five -- by preventing their
rescue—or allowing the five to be rescued. In the latter case, if the five are rescued, it
won't be Homer's doing, but in the former, if the five are saved, it will be the Fat Man
who saves them, even if involuntarily.
Killing people when one has the alternative of letting them live is, other things being
equal, plain murder. But the Fat Man's choice of whether to defend himself is between
killing people versus preventing their death, and we view cases like these as morally
different.
The most famous example of a dilemma like our Fat Man's is Judith Jarvis Thomson's
Violinist case7.
THOMSON'S VIOLINIST
You are knocked unconscious and kidnapped. When you wake you find
your circulatory system is plugged into the body of a sickly violinist. The
police have apprehended the kidnappers. They were fans of the violinist
7
Thomson, J. "A Defense of Abortion". Philosophy and Public Affairs 1:1 (Autumn 1971): 47–66.
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who were trying to keep him alive. You are now free to go, but you are told
that if you unplug yourself, the violinist will die. Only if you remain hooked
up to the violinist for many months does the violinist have any chance of
survival.
In Thomson's story, your choice is between unplugging-- and thus causing the death of
the violinist,--or sacrificing months of your life to prevent the violinist from dying.
Thomson thought that, while it would be admirable of you to play the Good Samaritan in
such a case, you were not morally obliged to do so. It would be permissible for you to
unplug.
While far fetched, Thomson's story was not frivolous. It was meant to be analogous to:
ABORTION
A woman is raped. She discovers that she is pregnant. Her choice is to
have an abortion or to bring the fetus to term.
Set aside the usual arguments about whether or not a fetus is a person. The violinist is
certainly a person, but if we think you are not obliged to stay plugged into him, why
should we think the rape victim is obliged to play Good Samaritan to the "person"
plugged into her?
People have conflicting intuitions about such cases, and intuitions can change when
variables vary (e.g., how long must one remain plugged in?). But there is a regularity in
everyone's responses which is captured by a principle that Kadri Vihvelin and I dubbed8
“The Deontological Equivalence Principle."
The Deontological Equivalence Principle
Causing a death when one's only alternative is to prevent it, is morally
equivalent to allowing a death when one has the alternative of preventing
it.
The Principle does not take sides on whether you may or may not unplug. Instead, it
predicts that you will think it impermissible to unplug yourself from the violinist only if
you think that you would have been obliged to plug yourself in if you had been asked
8
Vihvelin, K., & Tomkow, T. (2005). The Dif. Journal of Philosophy,102(4), 183-205.
doi:10.5840/jphil2005102420
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ahead of time. Alternatively, if you think morality does not require you to sacrifice
yourself to save others, then you will think that morality permits you to cause their death
when your only alternative is to sacrifice yourself to save them. Or again, if you think it is
very, very bad, but not murder, to refuse to make a small sacrifice to save a life then
you will think it just as bad, but not worse, to cause a death when, with the same
sacrifice, you could prevent it.
If you think the Fat Man is morally obliged to throw himself onto the track to save the
five, then you will think it equally wrong for him to prevent Flanders from pushing him.
On the other hand if like most of us, you think that the Fat Man is not required to throw
himself in front of the trolley, you will agree that he is not obliged to let Flanders push
him in front of it.
If that is right, then it is morally permissible for the Fat Man to defend himself against the
push, just as it is permissible for him to refrain from jumping on his own. And that means
the Fat Man does have the right to self-defense even though the Lone Man on the
siding does not.
And we may note that the same arguments apply to all the cases to which Fat Man is
sometimes compared. Thus:
FORCED TRANSPLANT
You learn that a doctor has plans to kidnap you and use your vital organs
to save the lives of five other people. But you have a gun…
UTILITARIAN JUDGE
You learn that a judge plans to hang you for a crime you did not commit in
order to prevent riots in which many people will be killed. But you have a
chance to escape…
In both these cases, your eluding the threat will lead to the death of innocent people, but
we may think that permissible given that your only alternative is to sacrifice yourself to
prevent those deaths.
What does all this show?
Well, there are some theories of self-defense that entail that a person has the right to
self-defense if but only if it is impermissible to harm them. Perhaps that is the theory
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that underlies the intuition that it is permissible to turn in TROLLEY but not in FAT MAN.
Then too, according to many accounts of self-defense, the right self-defense entrains
the right of "other-defense"; so that if someone is permitted to defend themselves
against an action, then others are likewise permitted to intervene to help them prevent
it. Perhaps, when folks express qualms about pushing the Fat Man, they are sensitive
to the fact that it may be permissible for third parties to forcibly restrain them.
Or, maybe, folks see a moral difference between, on the one hand, saving the lives of
five people and, on the other, forcing someone else to save those lives.
Perhaps, at the end of the day, we'll decide that folk's reasons, whatever they are, are
not good. But to be entitled to that conclusion we'll have to work a lot harder at
understanding the reasons folks say what they do.
Folks are smart; smarter than philosophers give them credit for. I recommend
philosophers do fewer experiments and use more imagination.