Thomson on The Trolley Problem

1. A Brief History of the Trolley Problem: Philippa Foot’s 1967 article, where she
pitched both Trolley and Organ Harvest kicked off a hugely important conversation in
ethics. In both cases, you kill 1 in order to save 5. Yet, nearly everyone thinks it
permissible to kill one in Trolley, and Impermissible to kill one in Organ Harvest. Why?

In Foot’s original version of Trolley, you’re the DRIVER. To Foot, the solution was simple:

In Trolley (Driver), you can kill 1, or kill 5 (and killing 1 is better than killing 5)
In Organ Harvest, you can kill 1, or LET 5 die (and killing 1 is WORSE than letting 5 die)

[Question: IS killing-1 worse than killing-5? Imagine an Organ Harvest variant where the
doctor has given 5 patients chemicals which have atrophied various organs. He needs to
kill the 1 innocent patient and harvest the organs in order to save the 5. If he does NOT
kill the 1, he will have killed the 5. So, he has a choice: kill-1 or “have-killed” 5. Thomson
thinks it would be WRONG to kill the 1. So, killing 1 is WORSE than killing 5 in this case?
Yes, this is the weirdness identified in Jason Hanna’s paper, inspired by Judith Thomson.]

Foot’s solution seemed fine, but then Thomson introduced the now far more familiar
version of Trolley (Switch). In both Switch and Organ Harvest, you can either kill 1, or let
5 die. Yet, killing one seems permissible in Switch, but wrong in Organ Harvest! WHY!?
Finally, Thomson replaced Organ Harvest with the famous Fat Man (or Footbridge) case:

Footbridge You are standing on a bridge above some trolley tracks. A runaway
trolley is hurtling down the tracks toward 5 people. A very large man stands next
to you on the bridge. You realize that his bulk would be enough to stop the
trolley. If you push him off of the bridge and onto the tracks below, he will die,
but the trolley will come to a halt and the 5 will be saved. Otherwise, the trolley
will hit the 5 and they will die.

Is it permissible to push the large man off of the bridge? Nearly everyone says ‘No’. But,
compare Trolley (Switch) vs. Trolley (Footbridge). In BOTH cases you can either kill 1 or
let 5 die. What is the difference? This is The Trolley Problem.

2. DDE to the Rescue?: Enter the DDE. Here is an obvious moral difference: In
Footbridge (as well as Organ Harvest), you are intentionally USING the large man as a
mere MEANS to an end. (Or, in Quinn’s terms, you are deliberately INVOLVING him in a
harmful event.) Meanwhile, in Trolley (Switch), you are not. The harm to the one on the
side track is merely foreseen as a side-effect of saving the 5.

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In both Footbridge and Organ Harvest, you NEED the one to die in order to accomplish
your goal. As Thomson defines it, “he uses the one to save the five only if, had the one
gone out of existence just before the agent started, the agent would have been unable
to save the five.”

3. Looping Trolley: Great! Trolley Problem solved! But wait. Now consider:

Looping Trolley Very similar to Trolley (Switch). There is a trolley headed toward
5 people, and you are standing near a switch that will divert the trolley onto a
side track, and there is 1 person on the side track. Two additions: (a) The man on
the side track is very large—large enough that his bulk would stop the trolley if it
hit him. (b) The side track loops around and back onto the main track.

You have two options: (i) Do nothing, and the 5 will die. (ii) Pull the lever, diverting the
trolley where it will hit the large man’s body and come to a halt. He will die, but his body
prevents the trolley from looping back around and killing the 5—so they will be saved.
What should you do?

Nearly everyone believes that (ii) is at least PERMISSIBLE (and perhaps even obligatory).

But, wait. You’re USING the body of the one on the side track as a MEANS to an end.
You NEED the trolley to hit him in order to achieve your goal. (Furthermore, you’re
deliberately involving him in a harmful event—namely, getting the trolley to hit his body
so that it does not hit the 5.) Thomson writes,

“the agent here needs the one (fat) track workman on the right-hand track if he is
to save his five. If the one goes wholly out of existence just before the agent
starts to turn the trolley, then the agent cannot save his five.”

Therefore, the harm is intended rather than foreseen; so, by the DDE, killing the 1 in
Looping Trolley is morally wrong in the same sense that killing the 1 is wrong in Organ
Harvest and Trolley (Footbridge)! But, that is absurd. Therefore, the DDE is false
(including Quinn’s version).

4. Biting the Bullet: Can’t we just admit that diverting the Looping Trolley is wrong?

Reply: Thomson thinks this admission would be absurd, writing,

“we cannot really suppose that the presence or absence of that extra bit of track
makes a major moral difference as to what an agent may do in these cases, and it
really does seem right to think (despite the discomfort) that the agent may proceed.”

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We can even alter Trolley (Switch) so that the man is very large, and the ONLY difference
between Switch and the Looping variant is the extra bit of track. Thomson asks: Can we
REALLY bring ourselves to accept that the extra bit of track makes the difference
between being a hero (as in Trolley) or a villainous murderer (as in Organ Harvest)!?

In a 2015 reply to Frances Kamm, she makes this answer seem even more preposterous:

“That strikes me as a thoroughly odd idea. It is the odder the larger the loop is in
Loop. Suppose the loop in Loop is twenty miles long. The possibility of a loop
connection twenty miles away—which would mark the [lever-puller] as the
bystander in Loop rather than as the bystander in Bystander—should make the
difference as to whether the [lever puller]’s turning the trolley, and thereby killing
the one, would be all right or all wrong?” (Trolley Problem Mysteries, 2015, p. 131)

Imagine that the side track went off into the distance and you WEREN’T SURE whether it
looped back around or not. As you pull the lever, you’ll think, “Well, if it loops back
around, I’m a moral monster. If it doesn’t, I’m A-Okay!” Thomson thinks this is ridiculous.

[Do you agree? Surely, Thomson should at least admit that a bit of extra track CAN make
the difference between being a hero and a monster. Imagine that there is one child on the
main track, and you can divert it onto a side track where the trolley will come to a halt
due to a gap in the track. There are TEN children just beyond the gap. Now compare this
case with a variant where there is NOT a gap, and diverting the trolley causes it to run
over the 10. One’s action seems permissible in the first case and wrong in the second,
surely—and all due to a bit of extra track!]

5. Thomson’s Solution: Judith Thomson rejects both the DDA and the DDE! Consider:

Hospital-1 A doctor can save 5 patients by operating on them, but this will
release a poisonous gas which kills a 6th nearby patient who cannot be moved.

Thomson and Foot are in agreement: It is clearly NOT permissible to operate. [Do you
agree?] But, notice, just like Trolley (Switch), you do not kill the one intentionally as a
means to saving the 5; rather the harm is merely a FORESEEN side-effect of saving the 5.
The following variant will help us understand Thomson’s solution:

Hospital-2 There are poisonous fumes headed through the ventilation toward a
room with 5 unmovable patients. You can close off a section of the duct to
prevent this. Unfortunately, however, this will divert the fumes into another
nearby room where it will kill 1 unmovable patient.

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Thomson thinks it permissible to divert the poisonous gas in this case. [Do you agree?]

In both Hospital-1 and Hospital-2, harm to the one patient is DO/FORESEE—yet, in the
former it is wrong, and in the latter it is permissible. What’s the difference?

We CAN’T appeal to the DDA’s claim that ‘killing 1 is worse than letting 5 die’ (for this
is false in both Trolley and Hospital-1). And we CAN’T appeal to the DDE, since
NEITHER Hospital-1 nor Hospital-2 are intended harm. So, what’s the difference?
Perhaps another pair of cases will help (inspired by two examples from her 1976, ‘Killing,
Letting Die, and the Trolley Problem’):

Missile-1 Terrorists have launched a missile at Richmond (pop. 200,000). The

only way to prevent the complete destruction of Richmond is to launch our own
attack on Charlottesville (pop. 40,000) as the terrorist missile passes over
Charlottesville’s airspace. The explosion that our own missiles create would be
enough to destroy the enemy missile as it passes by. The president orders our
military to attack Charlottesville.

Missile-2 Terrorists have launched a missile at Richmond (pop. 200,000). The

only way to prevent the destruction of Richmond is to divert the missile.
Unfortunately, if the missile is diverted, it will hit Charlottesville (pop. 40,000)
instead. The president orders the bomb to be diverted.

Thomson thinks that the president’s action in Missile-2 is wrong, but permissible in
Missile-1. [Do you agree?] Are you starting to see a pattern? Thomson writes,

“In Bystander at the Switch, something threatens five, and if the agent proceeds,
he saves the five by making that very thing threaten the one instead of the five. …
[He] does not make something be a threat to people which would otherwise not
be a threat to anyone; he makes be a threat to fewer what is already a threat to
more.”

This is also true of both Hospital-2 and Missile-2. There is a threat which is going to kill
some people NO MATTER WHAT. It is “up for distribution” so to speak. In such a
scenario, Thomson thinks it is permissible to distribute the threat in such a way that it
does as little harm as possible.

This is NOT how things are in Organ Harvest, Footbridge, Hospital-1, or Missile-1,
however. In each of those cases, the agent creates a NEW threat. This is much worse,
morally, according to Thomson.

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Thomson’s proposal seems to be something like this:

Thomson’s Doctrine: All else being equal, it is (at least sometimes) much worse,
morally, to harm by making something be a threat which would not have
otherwise been a threat than it is to produce the same amount of harm by
making a pre-existing threat to more be instead a threat to fewer.

The Solution to Looping Trolley: Whereas Looping Trolley was a problem for the DDE, it
is NOT a problem for Thomson’s doctrine. For, in both Trolley (Switch) AND Looping
Trolley, you are merely making something which threatens 5 threaten 1 instead—and
this is permissible.

6. Objection: Wait… But, you don’t introduce a new threat in Footbridge! Rather, you’re
making the trolley (a pre-existing threat) threaten one (fat man on the bridge) rather
than five (on the tracks)! So, on Thomson’s proposal, pushing the fat man is permissible?

Reply: Thomson adds: It is permissible to make it such that a threat will do less harm,
PROVIDED THAT doing so does not violate anyone’s rights—but pushing someone off
of a bridge clearly violates their rights. She writes,

“it is true of this agent, as it is true of the agent in Bystander at the Switch, that he
saves his five by making something which threatens them instead threaten one.
But this agent does so by means which themselves constitute an infringement of
a right of the one's. For shoving a person is infringing a right of his. So also is
toppling a person off a footbridge.” (1409)

In short, she seems to be ADMITTING that pushing the fat man off of the bridge is
merely an instance of re-distributing a pre-existing threat. But, it’s still impermissible
because you re-distribute the threat in a way that violates his rights.

Rebuttal: Um… Doesn’t diverting a trolley onto someone violate their rights, too?
Imagine that there is NO ONE on the main track, and you just divert a trolley onto the
side track where it kills one person. CLEARLY you have violated this person’s rights,
haven’t you? (namely, their right to life) In short, both diverting a trolley onto someone
AND pushing someone in front of a trolley violate the victim’s right to life. 1

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Brainstorm: Thomson might try to claim that, somehow, in Trolley (because there ARE 5 on the main
track), diverting the trolley does NOT violate the rights of the one on the side track. But, why would this
be? Possible answer: Because such a right doesn’t exist when one is making a pre-existing threat go from
threatening more to threatening fewer? But, then, this is also true of the Footbridge case!

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Reply: Thomson claims that pulling the lever is NOT a rights-violation! She writes,

“turning the trolley onto the right-hand track is not itself an infringement of a
right of anybody's. The agent would do the one no wrong at all if he turned the
trolley onto the right-hand track, and by some miracle the trolley did not hit
him.”

[But, literally 5 pages earlier, when discussing Trolley vs. Organ Harvest, she wrote,

“Is it clear that the bystander would infringe no right of the one track workman's
if he turned the trolley? Suppose there weren't anybody on the straight track, and
the bystander turned the trolley onto the right-hand track, thereby killing the
one, but not saving anybody, since nobody was at risk, and thus nobody needed
saving. Wouldn't that infringe a right of the one workman's, a right in the cluster
of rights that he has in having a right to life? So should we suppose that the fact
that there are five track workmen on the straight track who are in need of saving
makes the one lack that right-which he would have had if that had not been a
fact? But then why doesn't the fact that the surgeon has five patients who are in
need of saving make the young man also lack that right?” (1404)]

A charitable interpretation: Perhaps she means to say that a MERE lever-pulling is not
itself a rights violation. Meanwhile a MERE shoving IS a rights violation. And her claim is
that it is generally permissible to make a threat harm fewer rather than more, provided
that the act of making thing threat harm fewer does not violate the rights of the fewer.

Rebuttal: Let’s modify Footbridge so that the fat man is merely NEXT TO the track so
that the shoving is not a shoving off of a bridge, but just a gentle push. Surely, gently
pushing someone is only a minor rights violation. Is it REALLY plausible to say that this
minor rights violation makes all the difference between heroics and murder?

Imagine further that, in Trolley (Switch), you ALSO had to commit a minor rights
violation; e.g., you had to lie to the one on the side track, or break your promise to pay
the victim $10, or whatever. Would this make any difference? Presumably not.

Reply: Thomson actually addresses this. She gives some examples where you have to
violate a minor right of the one in Switch in order to direct the trolley onto him. For
instance, imagine that you have to trespass across his land to get to the lever (say, as a
shortcut), or you have to use a tool of his to move the lever (say, a wrench or a cane). In
each of these cases, you violate the victim’s property rights. Would it still be permissible
to pull the switch and divert the trolley? Thomson answers,

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 “For my own part, I do not find it obvious that he may. (Remember what the
bystander will be doing to the one by throwing that switch.) But others tell me
they think it clear the bystander may proceed in such a case. If they are right—
and I guess we should agree that they are—then that must surely be because the
rights which the bystander would have to infringe here are minor, trivial, non-
stringent-property rights of no great importance. By contrast, the right to not be
toppled off a footbridge onto a trolley track is on any view a stringent right.”

Rebuttal: So, ultimately, she’s appealing to the fact that a toppling OFF A BRIDGE is a
pretty major rights violation. Except that we’ve altered the Fat Man case so that he is
merely BESIDE the track. Surely, the right to not be shoved is quite trivial?

Possible Reply: When referring to one side of the distinction as:

“makes be a threat to fewer what is already a threat to more”

Could she instead refer to:

diverting a pre-existing threat, so that it threatens fewer/less harm (?)

While pushing the fat man DOES make the trolley threaten fewer rather than more, it is
NOT an instance of diverting a pre-existing threat. Rather, you are “diverting” the fat
man so to speak! [Could it really matter, morally, whether you get the trolley to threaten
the fat man by moving the trolley into the man vs. moving the man into the trolley?]

A Final Objection: Consider this case:

Trolley Initiator Exactly like Switch, except that, rather than DIVERTING the
trolley onto a side track where it will kill one, it instead brings the moving trolley
to a halt, and starts up a second trolley on a separate track, where it will kill one.

Is it permissible to throw the switch in this variant? It would seem so. [Do you agree?]
But, Thomson’s proposal entails that it is more like Organ Harvest than Trolley (Switch).
You are generating a NEW threat, so your action is morally wrong. Since this is absurd,
Thomson’s proposal is false.

7. Other Considerations: Two other minor points:

Special Claims: Surely SOME rights violations will render pulling the lever in Trolley
impermissible. For instance, imagine:

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 Trolley (Mayor at the Switch) Like Trolley (Switch), but you’re the mayor and
you’ve personally guaranteed to the people that the side-track is defunct, and
even arranged for a picnic to be held there.

Is it permissible to divert the trolley?

Individuation: Depending on how we individuate things, it WON’T be the “same thing”

that threatens. For instance, perhaps in Switch, it is the left half of the trolley that kills
the 5, but the right half which will kill the 1 if the trolley is diverted. Perhaps you ARE
introducing a new threat by diverting the trolley after all!

(Or, consider: Perhaps, in Bernard Williams’ Jim and the Indians, the same gun will be
used no matter who is killed. So do you really introduce a new threat by killing the 1
rather than allowing Pedro to kill all 10?)

Thomson merely dismisses this worry, saying surely there’s some distinction in the
ballpark of “same threat” to be made sense of.