By Daniel Sokol

Suppose you could save five lives by taking one - what would be the correct thing to do? Such ethical dilemmas provide classic "experiments" for philosophers. Here the Magazine presents four such quandaries and asks readers to vote on what they think is right. [Magazine note: apologies but we have had a technical hitch with the votes. We've replaced the vote modules, and will add those already cast to the totals.] Like scientists, philosophers use experiments to test their theories. Unlike scientists, their experiments do not require sophisticated laboratories, white-robed technicians or even rodents. They occur in the mind, and start with 'What if...'. These "thought experiments" help philosophers clarify their understanding of certain concepts and intuitions. In the field of ethics, thought experimenters typically present a dilemma, examine the most popular "intuitive" response and then show the implications for real-world issues. But such experiments are rarely tested on large numbers of people. So to reach a larger group, here are four typical experiments. Readers are invited to vote on how they think they would act in each case. Here is a well-known example: 1. THOMSON'S VIOLINIST One day, you wake up in hospital. In the nearby bed lies a world famous violinist who is connected to you with various tubes and machines. VOTE RESULTS Do you have an obligation to stay connected? Yes 30.62%

No 69.35%

3765 votes cast Results are indicative and may not reflect public opinion To your horror, you discover that you have been kidnapped by the Music Appreciation Society. Aware of the maestro's impending death, they hooked you up to the violinist. If you stay in the hospital bed, connected to the violinist, he will be totally cured in nine months. You are unlikely to suffer harm. No one else can save him. Do you have an obligation to stay connected?

The creator of the experiment, Judith Thomson, thinks the answer is "no". It would be generous if you did, she claims, but there is no obligation to stay, even if that means the violinist will die. So how is this bizarre scenario related to the real world? Thomson used the experiment to show that a pregnant woman need not go to full term with her baby, as long as she had taken reasonable steps to avoid getting pregnant. It is thus a "pro-choice" argument. The violinist represents the baby, and you - in the hospital bed - play the role of the mother. If you think unhooking yourself from the violinist is acceptable, but aborting an unwanted foetus is not, what are the moral differences between the two cases? In both situations, you could save a person by bearing a great burden for nine months. One major flaw with thought experiments, especially in ethics, is that they are rarely tested on people. The sample size is minuscule. The philosopher will simply assume that most people think that one option is right (or wrong). Philippa Foot, a renowned British philosopher, believed that if a doctor, about to save a patient's life with a large dose of a scarce drug, was suddenly interrupted by the arrival of five patients each in need of one fifth of the drug (without which death would be certain), then the doctor should give it to the five. It is, after all, better to let one person die than five. Elizabeth Anscombe, another prominent philosopher, disagreed: "There seems to me nothing wrong with giving the single patient the massive dose and letting the others die". As these assumptions about people's intuition are central to the arguments of many philosophers, and as these assumptions can be tested, why not do so? 2. THE RUNAWAY TROLLEY CAR One of the most famous thought experiments in ethics is "the runaway trolley". It aims to clarify how we should distinguish right from wrong. Here is the scenario with two well-known variations. VOTE RESULTS Should you flip the switch? Yes 76.85%

No 23.15%

3814 Votes Cast Results are indicative and may not reflect public opinion A runaway trolley car is hurtling down a track. In its path are five people who will definitely be killed unless you, a bystander, flip a switch which will divert it on to another track, where it will kill one person. Should you flip the switch?

3. THE FAT MAN AND THE TROLLEY CAR The runaway trolley car is hurtling down a track where it will kill five people. You are standing on a bridge above the track and, aware of the imminent disaster, you decide to jump on the track to block the trolley car. Although you will die, the five people will be saved. VOTE RESULTS Should you push the fat man? Yes 26.88%

No 73.12%

20320 votes cast Results are indicative and may not reflect public opinion Just before your leap, you realise that you are too light to stop the trolley. Next to you, a fat man is standing on the very edge of the bridge. He would certainly block the trolley, although he would undoubtedly die from the impact. A small nudge and he would fall right onto the track below. No one would ever know. Should you push him?



Philippa Foot would say that everyone ("without hesitation") would choose to flip the switch in the first trolley case, but that most of us would be appalled at the idea of pushing the fat man. The philosophical puzzle is this: Why is it acceptable to sacrifice the one person in The Runaway Trolley Car but not in The Fat Man case? Can it ever be morally acceptable to kill an innocent person if that is the only way to save many? Should some actions - such as deliberately killing innocent people against their wishes - never be done? The last thought experiment explores this idea: 4. THE CAVE EXPLORERS An enormous rock falls and blocks the exit of a cave you and five other tourists have been exploring. Fortunately, you spot a hole elsewhere and decide to let "Big Jack" out first. But Big Jack, a man of generous proportions, gets stuck in the hole. He cannot be moved and there is no other way out. VOTE RESULTS Should you blast Big Jack out? Yes 74.12%

No 25.88%

19377 votes cast Results are indicative and may not reflect public opinion The high tide is rising and, unless you get out soon, everyone but Big Jack (whose head is sticking out of the cave) will inevitably drown. Searching through your backpack, you find a stick of dynamite. It will not move the rock, but will certainly blast Big Jack out of the hole. Big Jack, anticipating your thoughts, pleads for his life. He does not want to die, but neither do you and your four companions. Should you blast Big Jack out? If the roles were reversed, what would you advise your trapped companions to do?

Thought experiments, although abstract, possibly implausible and open to different interpretations, can have important repercussions on the way we think and act as individuals. They raise thorny questions about morality in medicine, war, politics and indeed in everyday life. Is there a difference between killing someone and letting them die? Are consequences all that matter, or are there some things we should never do, whatever the outcome? By pointing out inconsistencies in our thinking, or simply encouraging us to reflect on issues we usually ignore, they can sharpen our intellect and enrich our moral lives. They also make for great conversation topics at the dinner table or at the pub. But be warned: you may lose friends as a result. And stay away from caves and bridges. Daniel Sokol is a medical ethicist at Imperial College, London. Add your comments on this story, using the form below. I feel sorry for the five people. Not only have they had a runaway trolley hurtling towards them but also got trapped in a cave. What a day!

Laura Kingdon, Cwmbran Surely the answer to the runaway trolley depends on the people involved. If it were the choice between five 90-year-olds and a single 20 year old, it would be right to save the 20 year old who, in probability, had longer to live than the others put together? Or what if those five were criminals and the other was a volunteer worker?

Joanthan Kelk, Dalry, Scotland It's interesting to compare this with the Iraq war - was it right through intervention to kill as many people as we have in order to save a far greater number that were dying and would continue to die under the regime. Usually people seem to say, no, as it is us pushing the fat man, despite the fact that five people arguably died through our inaction.

Brian, England In the case of the Runaway Trolley Car, I would definitely NOT flip the switch. The end doesn't always justify the means.

Jenny, Leeds In the examples given we must assume that all involved people are equal. However, would it be right, good or efficent to kill one superior person to save four lesser people? I do not of course mean by race or any such thing but by worth to the whole. If the one person was a brilliant doctor developing a cure for cancer, would you divert the trolley towards him to save four? What about ten? Fifty? A thousand people crammed onto a train car packed with explosives?

Chris Fox, Derby I'd use the dynamite to blast the trolley off the rails and then hook the violinist up to the fat man.

Robin, Edinburgh Thomson's violinist is not the same principle as abortion. If you choose to disconnect yourself you are in essence withdrawing treatment, that is refusing to intervene to save the life of someone who would otherwise die. In an abortion you're choosing to deliberately end the life of someone who would otherwise live.

Kate I would like to point out a problem I have with the direct application of the violinist thought experiment, as presented above, to the case of abortion. In the experiment, if the violinist chooses to stay connected, they need have nothing to do with the violinist once the nine months have elapsed. If a woman is pregnant, and chooses to keep the baby, they will have to bring the baby up - with important consequences for her life, that of the baby, and that of those close to her - or give the baby up for adoption - which again is likely to affect her strongly and will certainly affect the baby.

Suzanne Aigrain, Cambridge If the violinist were my son or daughter I would not hesitate to stay connected. (Maybe when they recover they will keep their rooms tidy to show their gratitude!)

Jack, Coventry Cave Explorers: I am a caver,and I can assure you that the smaller six people definitely would NOT let Big Jack out first- he'd be forced to go last in order to avoid the very situation described...

Jane, Epsom It's your birthday. Four of your friends together buy you one lottery ticket as a present. You win £5 million. Do you share the money with these friends, who only spent £0.25 each on your birthday present?

Jagdip Singh Ajimal, Manchester These situations in reality aren't as black and white as a yes or no answer - different people will respond differently and for different reasons, and no one is necessarily right or wrong. However, in reality getting involved in choosing who survives will likely get you sued or arrested!

Hannah, Wokingham I really enjoyed the puzzle dilemmas, but I thought that the five people should die in the runaway trolley car as it's their fate; flipping the switch would be intentional murder. Also, if I wasn't there to flip the switch they would have died anyway- so its all fate!

Ayelee, London You can only flick switches if you have a perfect understanding of the future, otherwise you might save a serial killer or kill a Nobel peace prize winner. It is an infinitely unpredictable world and philosophical conundrums cannot take account of this. As for Big Jack, he's history, primal instincts would take over from philosophy, the only decision to make is where to put the dynamite.

Julian, Shrewsbury Would you injure Rooney and put him out of the world cup, or would you rather Gerrard and Lampard and Terry all were injured?

Tak Joss, Guildford Name

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