Politics, Philosophy, Polemics

Archive for the ‘Thought Experiments’ Category

On Trolleys, Bazookas, and Faulty Reasoning

In Jewish Matters, Philosophy, Thought Experiments on November 30, 2014 at 8:59 PM

The so-called trolley problem, which single handedly appears to have kept a generation of moral philosophers in a job, is now well known. The problem, simply put, is why the intuitions of many as to the correct course of action differ between the following two cases which I have paraphrased from Judith Jarvis Thomson’s 1985 paper, “The Trolley Problem”:

Bystander at the switch

An out of control train is headed down a track and is on course to kill five people. You are an innocent bystander standing at a switching point.  If you flick the switch, the train is diverted to a spur track. The five people will be saved but unfortunately, there is one person tied to the spur track and he will die. Should you flick the switch?

Fat Man

An out of control train is headed down a track and is on course to kill five people. You are an innocent bystander standing on a footbridge over the track. Next to you, standing precariously on the edge of the footbridge, is a fat man. If you give the fat man a little push he will fall onto the track and his weight will stop the train and hence prevent the five from being killed. Unfortunately, the fat man dies. An act of self-sacrifice such as jumping off the bridge yourself would not work as your own weight is not sufficient to stop the train.  Should you push the fat man?

Much on the literature on this problem is to try and explain and justify the authors’ views, in line with the intuition of many, why it is acceptable to kill one to save five in Bystander at the switch but not acceptable to kill one to save the five in Fat Man.

However, Judith Jarvis Thomson had a paper published in 2008 entitled “Turning the Trolley” where she admitted that she had changed her view. She now thought it wrong to flick the switch in Bystander at the switch. She constructed a new thought experiment that I paraphrase below:

Bystander’s Three Options

An out of control train is headed down a track and is due to kill five people. You are a bystander standing on a left hand spur. There is also a workman on right handed spur track. Your three options are (i) do nothing in which case five people die, (ii) flick the switch to the right in which case the only person who dies is the workman on the spur, or (iii) flick the switch to the left killing yourself and no one else.

Thomson reasons: “I hope you will agree that choosing (ii) would be unacceptable on the bystander’s part. If he can throw the switch to the left and turn the trolley onto himself, how dare he throw the switch to the right and turn the trolley onto the one workman?” She goes on to explain that self-sacrifice is not required: “[A man] may let five die if the only permissible means he has of saving them is killing himself.”

It is this version of one of the many trolley problem thought experiments that is taken up by Howard Nye in his paper: “On the Equivalence of Trolleys and Transplants: The Lack of Intrinsic Difference between ‘Collateral Damage’ and Intended Harm,” just published in the December 2014 issue of Utilitas. (Sadly, the link requires a subscription. It is not free to access.) Nye explains that he was convinced that Thomson’s Bystander’s Three Options was equivalent to his own thought experiment below:

Bazooka Holder’s Three Options.

You, Bugsy and the five are tied to three parallel trolley tracks, and empty trolleys are heading down each track. You have a bazooka with only two rounds, giving you three options: (1) blow up the trolleys heading towards the five and Bugsy, in which case only you will die; (2) blow up the trolleys heading towards the five and you, in which case only Bugsy will die; or (3) blow up the trolleys heading towards Bugsy and you, in which case only the five will die.

The problem is that these examples are not similar enough. There is a key moral difference and it has to do with the acts and omissions doctrine. This should not be elided without reasoning. These differences can be noted:

  1. Doing nothing in Bystander’s Three Options mean five people die, whereas doing nothing in Bazooka Holder’s Three Options means seven people die. This option of doing nothing is not noted by Nye as one of the bazooka holder’s three options. Doing nothing is noted as an option by Thomson in Bystander’s Three Options.
  2. Five people dying and no one else dying in Bystander’s Three Options results from doing nothing. The five people dying and no one else dying in Bazooka Holder’s Three Options results from the bazooka holder doing something: choosing to save himself and save Bugsy.
  3. Only one person (not the bystander) dying in Bystander’s Three Options results from doing something that kills the man on the spur. Only one person (not the bazooka holder) dying in Bazooka Holder’s Three Options results from the bazooka holder doing something to save the five and save himself. The Bazooka holder lets Bugsy die, he does not kill him.
  4. Only the bystander dying in Bystander’s Three Options results from the bystander committing suicide. Only the bazooka holder dying in Bazooka Holder’s Three Options arises from the bazooka holder choosing to saving six other people and letting himself die.

These differences are important. It is a well established relevant moral fact that there is a difference between killing a man and letting him die. It is crucial in many areas, notably the debate on euthanasia. It is also important in law: the difference between killing a man (drowning him in a river) and not saving his life (a bystander with no special duty of care not throwing a lifebelt to a drowning man) is the difference in countries such as England and America between going to prison for many years for murder or manslaughter and getting off scot-free.

Recall that Thomson argues that a man “may let five die if the only permissible means he has of saving them is killing himself.”  In response, Nye states:

It is indeed plausible that it is wrong to force a cost on someone if she isn’t morally obligated to assume it. There are, however, cases in which we do seem permitted to do things that result in someone’s bearing a cost that she would not be obligated to assume herself. We seem permitted, in cases like Bazooka Holder’s Three Options, to save ourselves rather than Bugsy even though Bugsy would not be required to save us rather than himself.

This is problematic because Nye has not made a comparable argument. In Bazooka Holder’s Three Options, if the Bazooka holder chooses to save the five and himself it is not what the Bazooka holder has done that results in Bugsy “bearing a cost” (dying). Bugsy dies because without any action on the Bazooka holder’s behalf he would die anyway.  Bugsy has no positive right that the Bazooka holder should save him.

While the five in Bazooka Holder’s Three Options also have no positive right to be saved, let us assume out of the goodness of your heart, you, the Bazooka Holder, used one of your bazooka rounds to save the five. If so, we are now left with the following problem.

Bazooka Holder’s Three Options (Revised)

You and Bugsy are tied to parallel trolley tracks, and empty trolleys are heading down each track. You have a bazooka with one round.  You have three options: (i) do nothing in which case you will both die, (ii) blow up the trolley heading towards yourself, saving yourself and letting Bugsy die, (iii) blow up the trolley heading towards Bugsy saving Bugsy and letting yourself die.

This revised problem is morally equivalent to the following:

Jug of Water

You and Bugsy are journeying through the desert and you have a single jug of water. You have three options (i) Share the water with Bugsy in which case you will both die as there is an insufficient amount to keep you both alive, (ii) give the jug of water to Bugsy such that he survives and you die, (iii) drink the water yourself such that you survive and Bugsy dies.

Some readers may be familiar with this version. It predates Judith Jarvis Thomson’s trolley problem by nearly two millennia. It arises in a dispute between Rabbi Akiva and Ben Petura on Leviticus 25:36. The answer to Jug of Water, according to Rabbi Akiva and Jewish law, is that you are not required to give up your own life so another might live. “Your life becomes before the life of your fellow man.” This is contrasted with a different Talmudic problem: Can a man threatened with death kill another man to save his own life?  The answer, according to the Jewish tradition, is no: “who shall say your blood is redder than his? Perhaps his blood is redder than yours.”

The point of me providing these last examples is not to promote Jewish ethical values, but to demonstrate that even in ancient times it was recognised that there is a moral difference between killing and letting die. This difference explains a crucial differential between Bystander’s Three Options and Bazooka Holder’s Three Options.

Philosophers and bizarre thought experiments, No. 4 – Lava

In Epistemology, Philosophy, Thought Experiments on January 18, 2014 at 8:17 PM

And some wonder why it is called the ivory tower:

Suppose that the mountain erupts, leaving lava around the countryside. The lava remains there until S perceives it and infers that the mountain erupted.  Then S does know that the mountain erupted. But now suppose that, after the mountain had erupted, a man somehow removes all the lava. A century later, a different man (not knowing of the real volcano) decides to make it look as if there had been a volcano, and therefore puts lava in appropriate places. Still later, S comes across this lava and concludes that the mountain erupted centuries ago. In this case, S cannot be said to know the proposition.


Alvin I. Goldman, “A causal theory of kn0wing,” in Sven Bernecker and Fred Dretske (eds.),  Knowledge: readings in contemporary epistemology, (Oxford: Oxford University Press, 2009), p.21.

Philosophers and bizarre thought experiments, No. 3

In Just War, Philosophy, Thought Experiments on July 4, 2013 at 11:41 AM

Jeff McMahan wrote a book, published in 2009, that sought to turn on its head what we understand about morality in war which is based on the centuries old tradition of Just War Theory. In the traditional theory, the morality of war is broken down into two major areas: just reasons for going to war (jus ad bellum) and just actions in the conduct of war (jus in bello). It is accepted that there is a moral equality of combatants. Hence, even if one side was unjustified in going to war, it does not mean that the combatants on that side are war criminals unless they commit unjust actions such as deliberately killing civilians.

This can be illustrated by a good example. It is not particularly controversial to say that the Allies were the just side in the war against Nazi Germany in World War II and the Nazi side were the unjust side. According to standard theory, Nazi soldiers who were involved in permitted actions of a soldier, such as fighting other armies and not killing civilians, are not doing anything morally wrong. This means that while SS officers who were involved in killing Jews were war criminals, Rommel’s Nazi troops who stormed around North Africa but obeying the rules of war such as proportionality and not deliberately killing civilians are not morally blameworthy.

McMahan thinks this is wrong. He thinks that an unjust war should not be participated in and that soldiers are morally blameworthy if they fight for an unjust side. He would view, contrary to the standard theory, Rommel’s Nazi troops as war criminals.

A conflict can occur when a just side would kill innocent civilian without intent but as a side effect of a just action. McMahan argues that while soldiers on an unjust side should not engage in combat with a just side, innocent civilians on the unjust side are permitted to defend themselves from harm resulting from actions of the soldiers on the just side. McMahan’s case is illustrated with a very bizarre thought experiment:

Suppose that just combatants are justified in destroying a storage facility for chemical weapons, but that the destruction of the facility foreseeably creates a cloud of toxic gas that will soon engulf an area inhabited by innocent civilians. If the civilians could somehow blow the cloud of gas away, they would be permitted to do that, even if their only option was to blow it over the just combatants, who would then be killed by it.


Jeff McMahan, Killing in War, (Oxford University Press, 2009), p.47.

Philosophers and bizarre thought experiments, No. 2

In Philosophy, Thought Experiments on May 5, 2013 at 7:13 AM

In article published in 2000*, the Harvard philosopher Frances Kamm considered the question of whether distance matters in a duty to rescue. The following two cases were reasonably mentioned:

Pond: I am walking past a shallow pond and see a child drowning in it. If I wade in and pull the child out, my $500 suit will be ruined. Intuitively, I ought to wade in to save him.

Overseas: I know there is a child starving to death overseas. To save him, I must send $500. Intuitively, I am not obligated to do so.

There is nothing too bizarre in either of those cases. However it was not to last. Reality went out of the window with this comment:

Suppose I stand in a part of France, but I have very long arms that reach all the way to the other end of France, allowing me to reach a child drowning in a pond at a distance….

*F.M. Kamm, “Does Distance Matter Morally to the Duty to Rescue?” Law and Philosophy, Volume 19, 2000, pp.655-681.

A Problem with Democracy

In Anarchism, Philosophy, Thought Experiments on February 23, 2013 at 7:03 PM

I have previously commented on my interest in thought experiments. Michael Huemer has posed a compelling one in his recent book, The Problem of Political Authority: An Examination of the Right to Coerce and the Duty to Obey (Palgrave Macmillan, 2013), p.59. The term “tyranny of the majority” was popularized by Alexis de Tocqueville as he used it in his important 1835 book, Democracy in America. Michael Huemer provides a neat example:

Imagine the following scenario, which I shall call the Bar Tab example. You have gone out for drinks with a few of your colleagues and graduate students. You are all busy talking about philosophy, when someone raises the question of who is going to pay the bill. A number of options are discussed. A colleague suggests dividing the bill evenly among everyone at the table. You suggest that everyone pay for his own drinks. A graduate student then suggests that you pay for everybody’s drinks. Reluctant to spend so much money you decline. But the student persists: ‘Let’s take a vote.’ To your consternation they proceed to take the vote, which reveals that everyone at the table except you wants you to pay for everybody’s drinks. ‘Well, that settles it’, declares the student. ‘Pay up.’

Philosophers and bizarre thought experiments, No. 1

In Abortion, Philosophy, Thought Experiments on December 1, 2012 at 7:39 PM

I have an interest in bizarre thought experiments that philosophers invent in the ivory tower. This blog is named after such a thought experiment, one whereby people are not born with eyes but obtain them when they walk under an ocular tree.  Two favourites of mine of those of which I am aware were used by Judith Jarvis Thomson  in her seminal 1971 essay, “A Defense of Abortion.” One of them involved someone being kidnapped and a famous unconscious violinist being plugged into their body for the rest of their life. The other involves “people-seeds” that drift into someone’s house through an opened window, attach to the carpet and grow into a “person-plant.” While these thought experiments are created to provide a point, the sheer bizarreness of them makes one wonder what was going through the philosopher’s head at the time.

I have just come across some more thought experiments, these ones written by Jonathan Bennett and published in his book, The Act Itself, (Oxford University Press, 1995), pp.209-211. Bennett is discussing the distinction between the foreseeable and intended consequences of an act. Using a thought experiment relative to the debate on abortion, he says the following:

it does not stop us from thinking that the surgeon intends the child’s head to be crushed but does not intend it to die, for the crushing does not absolutely, conceptually entail the dying: there are worlds where God steps in and restores the ruined head to its former condition, and others where crushing a head is the first step in a helpful curative procedure.

So much for crushing heads, how about killing people by terror bombing?

I said that the [terror bombing] raid leader intended to kill civilians so as to lower enemy morale, but the truth is finer grained than that. Really, he intended only that the people’s bodies should be in a state that would cause a general belief that they were dead, this lasting long enough to shorten the war: nothing in that scheme requires that the dismaying condition of the bodies be permanent; so nothing in it requires that the people become downright dead rather than merely seemingly dead for a year or two.

Bennett is now is full absurdity mode:

…the arsonist who does not intend the building to be permanently destroyed, just that it be reduced to ashes long enough for the insurance company to pay up.

This, dear reader, is the sort of thing that is discussed in philosophy departments of some of the world’s leading universities.