Moral Minds and the Trolley

I would like to pose a scenario to you reader.  You are rushing toward a platform next to a train track and a trolley is approaching in the distance.  You know that this trolley is unmanned, and it's brakes controlled by an automated system devised by an evil genius.  There is a man on the platform facing away from you, blindfolded, with duct tape over his mouth.  He stands there in a drugged stupor, and you know that the evil genius has surgically implanted a device next to the man's heart that when damaged or detects the man's heart beat stopped, will cease to respond to the automated trains' wireless queries.  The train is programmed to instantly apply it's brakes and come to a screeching halt if this happens.  Five people are trapped on the tracks a short way down past the platform, and will surely die if the trolley is not stopped.

You also have a gun.  You are five feet from the man on the platform, and you can shoot him in the heart in time for the train to stop.  You don't have time to do anything else.  The evil genius has devised a cruel scenario for you, but only you can save those people.  There are no other options, and time is running out.  You must kill this stranger, or be responsible for not avoiding the deaths of five others.  What will you do?  Will you kill the one man, or let the others die?  Remember your answer for later.

I recently started reading Moral Minds, a book about exploring the evolutionary roots of the morality found in humans and other animals.  In the third chapter, the author brings up the trolley problem originally posed by Philippa Foot.  You can get more background in this video if you're not familiar, but the gist of it is posing two different questions about killing one person to save five where people typically answer one way to the first scenario, but another in the second despite the fact that the outcome is the same.  I've seen this scenario referenced a lot lately, and something about it and what some have deduced from it have seemed off to me.

One explanation I have read previously was that the reason people answer differently is, the personal act of pushing the large man into the trolley's path engages an emotional part of our brains whereas the more detached act of pulling a lever to divert the train does not. Therefore, we judge the situation more logically.  In this chapter of Moral Minds, the author poses a different possibility, that the actual reason is that we have an innate moral sense that tells us intentionally killing someone as a means to save others is not permissible, but saving others in a way that results in the side effect of someone else being killed is.

To further convince us of this point, the author also poses some slightly adjusted scenarios.  In a third scenario, you may switch a lever to cause the trolley to be briefly diverted to a side track where the large man is on the tracks just before it rejoins back to the main track where the 5 other people are.  He states that this scenario is intuitively impermissible to us because we are intentionally causing harm to the large man to save the others.  Then, in a fourth scenario, he poses that again there is a short side track you can divert the trolley to before it joins back to the main track where the 5 people are.  This time though, the side track has a huge block on the tracks as big as the train that just happens to have one person in front of it that will accidentally get killed if you divert the train into the block to stop it.  This scenario he states is intuitively permissible because the death of the person is an unintended side effect.

Through these explanations, I continued to feel that something was wrong, and at some point I realized what it was.  I think that the real reason we judge these scenarios differently is related to a constant awareness of physics that we cannot avoid taking into account regardless of if we are told the large man's bulk will stop the trolley.  I believe that in our minds we aren't convinced that the large man will fully stop the trolley, and there will be some chance that the trolley will still kill some or all of the other people.  This applies in the third scenario as well, all illustrations that are used for these scenarios picture the people sufficiently close to whatever is being used to obstruct the trolley's movement to leave that bit of doubt in your mind.

I came up with another scenario that may be able to confirm my suspicion.  It is the scenario I posed at the beginning of this post.  If most people intuitively feel that it is not permissible to shoot the man to stop the trolley, then I must be wrong.  If most people think it is permissible, I think maybe our minds are doing some subconscious value calculations of the probabililities of numbers of people dying in these posed scenarios rather than following some odd rule of intentions.  Please share what you chose to do in that first scenario in the comments so we can do a mini-study!


  1. I would shoot the guy, but I'm aware of the thought experiment from something I read or heard previously (maybe RadioLab?) so that may be influencing my choice. Needless to say, the act of doing so would probably mess me up a lot and give me post traumatic stress, but I'm pretty sure that's what I would do.

    I don't know if physics enters into the equation, though... for me it's just utilitarian.

  2. Yeah, hearing both scenarios does affect people's later judgement in a lot of cases. Thanks for weighing in anyway though.

    In the scenario I made up, I was specifically trying to eliminate the potential for subconscious physics estimations to affect judgement.