Towards the end of this past semester, I was at dinner with one of my professors, and found myself debating at some length a question of morality. I’m sure most of you are familiar with Sophie’s Choice—a book, a movie, and a dilemma: you’re a mother with two children and are told to pick which one will die and which will live, or else both will be killed.

Philosophers have a similar thought experiment that removes a bit of the complicated sentiment that Sophie’s Choice is so rife with, broadly called “Trolley Problems” (one of the most famous thought experiments—this list and the descriptions are actually quite good, despite what the ‘z’ in the domain name might indicate). The thought experiment my professor offered me in this particular discussion is slightly different, but the general premise holds.

You are alive during Manifest Destiny era America, and you and twelve fellow settlers are traveling west in hopes of finding some nice land that doesn’t belong to you. You do not know any of your companions, as you signed on to the trip at the last minute. In the middle of the night, a band of Native Americans descend on your caravan and tie up all thirteen of you before any resistance can be offered. The chief of the tribe rides up to the group and lectures you about being Western Imperialist Asses.

Then he has you untied and brought before the group. His warriors stand behind each of your twelve companions. He hands you a rifle and pulls up one of your companions, whom he tells you to kill. If you do, the remaining twelve of you will be set free to go home and live out the rest of your Entitled-White-Man lives. If you do not, all twelve of your companions will be killed. It is important to note that, either way, you will survive. This Chief is very clever; he doesn’t want you to be motivated by a selfish desire to live.

Before we talk about what your options are here, we need to talk about a spectrum of moral culpability that moral philosophers use to explain the justification, or lack thereof, of an action. In simplest terms, the spectrum of culpability goes like this (from most culpable to least): inexcusable, understandable, excusable, justifiable, and praiseworthy. (These categories are not always mutually exclusive, because some of them operate slightly independent of the others, but this spectrum will do for our purposes.)

An inexcusable act is one that we belief to be absolutely and abhorrently wrong, like shooting up a crowd of innocent people for selfish reasons. No real discussion here. Guy’s just awful.

An understandable act is one that is still inexcusable (insofar as it must still be punished as morally wrong), but one about which we can nonetheless recognize a common ground and empathize with the motivations of the perpetrator of the act. Like hunting down the man who killed your wife. We have to say the act is wrong, but we kind of get why you did it.

An excusable act is one that is both understandable and somehow warrants the disregard of normal moral and legal standards. For example, if you were walking down the street and happened upon Osama bin Laden, totally helpless and at your mercy, it would be excusable for you to kill him if you knew he would otherwise escape prosecution or punishment and your motivation was to bring him to some form of justice. It would normally be wrong to kill a defenseless person in retribution like this, but because of the chance of his escape and the gravity of his crimes, our justice system would not charge you with murder and you would be hard pressed to find someone who thought you did the wrong thing.

A justifiable act is a bit different, but the distinction is subtle. A justifiable act is not just one in which we set aside general morality, but one for which the scale actually tips such that we believe you have indeed done nothing wrong. If someone has a gun drawn on you and clearly intends to kill you, you are justified in shooting him first. There is no immoral act to ‘excuse’ because we already believe killing in self-defense to be justified, as a rule.

A praiseworthy act is stronger still. A praiseworthy act is one in which you have actually done something laudable; an act that might, in isolation, be wrong, but because of the circumstances makes you a ‘better’ person because of it. Killing someone who is in the midst of a shooting spree, and thereby preventing many immediate deaths, is a praiseworthy act.

Now that we have painted these distinctions, we can come to the question at hand. My professor argued that you would be excused in killing one of your companions in order to save the other eleven of you. I agreed. The problem we had was with the converse: she believed that you would be justified for not acting at all. I disagreed.

Just to be clear: the Chief tells you to kill someone to save twelve, and we both agree that you are excused of wrongdoing in this act of murder. But I believe that, furthermore, it would be inexcusable for you not to act. I believe that not acting makes you complicit in the death of the thirteen.

Why should this be? I think the reason lies in your motivation for not acting, so let’s try and see if we can explain what that motivation might be. More people clearly die if you do not act. Eleven is greater than one. The math checks out. So your motivation cannot be to save life. The motivation is that you do not want to be the person to pull the trigger. I believe this to be an inexcusably selfish motivation.

Let me explain. I believe that your motivation for not pulling the trigger is that you do not want to live with the guilt of the act of what you perceive to be the killing of a defenseless and undeserving victim. This guilt may come from a belief that what you are doing is wrong, and this may be a justified guilt if you believe that the act of killing is wrong. But not acting will be to avoid this guilt, and that is a selfish act.

What I am talking about, then, is mandated sacrifice (in situations where the stakes are high enough). And no matter how you cut it, the stakes are always high enough in this example. Even if you had to kill eleven to save one, the stakes are still high enough, because you are still saving a life. Your guilt does not balance the matter.

My professor argued that the motivation for not doing so is that you do not want to make yourself complicit in an immoral act, and it is your belief that you are doing the right thing that guides your choice (not the guilt), so your inaction is justifiable.

But you are complicit either way. If you do not act, the others will die. Death will result from either choice, so your complicity is unavoidable. In one, you do not pull the trigger, yes; but why should this matter? We have already established that there are justifications for killing, so it cannot be that we think killing under any circumstances is inexcusable. The problem is you do not want to be the one to do it.

To highlight and defend my point, let’s turn briefly to an actual trolley problem. Five people are tied to a train track with a trolley approaching. On an alternate track, one person is shackled. You have a switch at your fingertips which will allow you to move the trolley from the track where the five are to the track with one, thereby saving the five and killing the one.

In another example, five people are once again tied to a track. Except this time you have no switch at your disposal. Instead, you have a very fat man that you can push off of a bridge and onto the track. This will kill the fat man, but save the five people. (I didn’t actually come up with this, so if you think I’m being insensitive, direct your grief to Judith Jarvis Thompson.)

Neuropsychologist Joshua Greene conducted a study showing that different sections of the brain operate in these different scenarios, a phenomenon he attributed to “emotion” getting in the way of the more immediate and real pushing of the fat man (as opposed to the somewhat sterile and distant act of flipping a switch). And both fMRI imaging and the numbers back this argument: more people were willing to flip the switch than push the fat man.

The number of victims in the respective scenarios don’t matter to us as much as the emotions of the act, so I do not think it is a strong deontology that is preventing you from firing the gun in the Indian Chief example.

We come back to guilt. You cannot get over the fact that you killed someone. But I believe this cannot possibly be weighed against the life of another person. Not acting is immoral because it leads to more death; even if you will feel worse about acting, you must. You must bear that burden. This is mandated sacrifice.

In my first article, I cited these trolley problems as being symptomatic of the trend of philosophers to be out of touch with what they need to be discussing with people. Is it hypocritical, then, for me to bring them up now? Am I retreating into the ivory tower?

I don’t think so. I’m trying to illustrate a larger point here. It may be that you feel bad about doing something, either because it will hurt someone you care about, or perhaps just because you are just too close to the situation. That doesn’t mean that you are excused from acting, that morality passes by or that the right thing has suddenly changed to accommodate sentiment. Morality is not so lenient.

It is a point summarized by Isaac Asimov in a rather elegant quip: “Never let your sense of morals prevent you from doing what is right.”