The Trolley Problem & The Prisoner’s Dilemma

Charles Carroll

Deontology & Kantian Ethics

9 The Trolley Problem & The Prisoner’s Dilemma

The Trolley Problem

Imagine you are standing beside some tram tracks. In the distance, you spot a runaway trolley hurtling down the tracks towards five workers who cannot hear it coming. Even if they do spot it, they won’t be able to move out of the way in time.

As this disaster looms, you glance down and see a lever connected to the tracks. You realise that if you pull the lever, the tram will be diverted down a second set of tracks away from the five unsuspecting workers.

However, down this side track is one lone worker, just as oblivious as his colleagues.

So, would you pull the lever, leading to one death but saving five?

This is the crux of the classic thought experiment known as the trolley dilemma, developed by philosopher Philippa Foot in 1967 and adapted by Judith Jarvis Thomson in 1985.

The trolley dilemma allows us to think through the consequences of an action and consider whether its moral value is determined solely by its outcome.

The trolley dilemma has since proven itself to be a remarkably flexible tool for probing our moral intuitions, and has been adapted to apply to various other scenarios, such as war, torture, drones, abortion and euthanasia.

Variations

Now consider now the second variation of this dilemma.

Imagine you are standing on a footbridge above the tram tracks. You can see the runaway trolley hurtling towards the five unsuspecting workers, but there’s no lever to divert it.

However, there is large man standing next to you on the footbridge. You’re confident that his bulk would stop the tram in its tracks.

So, would you push the man on to the tracks, sacrificing him in order to stop the tram and thereby saving five others?

The outcome of this scenario is identical to the one with the lever diverting the trolley onto another track: one person dies; five people live. The interesting thing is that, while most people would throw the lever, very few would approve of pushing the fat man off the footbridge.

Thompson and other philosophers have given us other variations on the trolley dilemma that are also scarily entertaining. Some don’t even include trolleys.

Imagine you are a doctor and you have five patients who all need transplants in order to live. Two each require one lung, another two each require a kidney and the fifth needs a heart.

In the next ward is another individual recovering from a broken leg. But other than their knitting bones, they’re perfectly healthy. So, would you kill the healthy patient and harvest their organs to save five others?

Again, the consequences are the same as the first dilemma, but most people would utterly reject the notion of killing the healthy patient.

Actions, Intentions and Consequences

If all the dilemmas above have the same consequence, yet most people would only be willing to throw the lever, but not push the fat man or kill the healthy patient, does that mean our moral intuitions are not always reliable, logical or consistent?

Perhaps there’s another factor beyond the consequences that influences our moral intuitions?

Foot argued that there’s a distinction between killing and letting die. The former is active while the latter is passive.

In the first trolley dilemma, the person who pulls the lever is saving the life of the five workers and letting the one person die. After all, pulling the lever does not inflict direct harm on the person on the side track.

But in the footbridge scenario, pushing the fat man over the side is in intentional act of killing.

This is sometimes described as the principle of double effect, which states that it’s permissible to indirectly cause harm (as a side or “double” effect) if the action promotes an even greater good. However, it’s not permissible to directly cause harm, even in the pursuit of a greater good.

Thompson offered a different perspective. She argued that moral theories that judge the permissibility of an action based on its consequences alone, such as consequentialism or utilitarianism, cannot explain why some actions that cause killings are permissible while others are not.

If we consider that everyone has equal rights, then we would be doing something wrong in sacrificing one even if our intention was to save five.

Research done by neuroscientists has investigated which parts of the brain were activated when people considered the first two variations of the trolley dilemma.

They noted that the first version activates our logical, rational mind and thus if we decided to pull the lever it was because we intended to save a larger number of lives.

However, when we consider pushing the bystander, our emotional reasoning becomes involved and we therefore feel differently about killing one in order to save five.

Are our emotions in this instance leading us to the correct action? Should we avoid sacrificing one, even if it is to save five?

Real World Dilemmas

The trolley dilemma and its variations demonstrate that most people approve of some actions that cause harm, yet other actions with the same outcome are not considered permissible.

Not everyone answers the dilemmas in the same way, and even when people agree, they may vary in their justification of the action they defend.

These thought experiments have been used to stimulate discussion about the difference between killing versus letting die, and have even appeared, in one form or another, in popular culture, such as the film Eye In The Sky.

The Prisoners’ Dilemma

By Avinash Dixit and Barry Nalebuff

The prisoners’ dilemma is the best-known game of strategy in social science. It helps us understand what governs the balance between cooperation and competition in business, in politics, and in social settings.

In the traditional version of the game, the police have arrested two suspects and are interrogating them in separate rooms. Each can either confess, thereby implicating the other, or keep silent. No matter what the other suspect does, each can improve his own position by confessing. If the other confesses, then one had better do the same to avoid the especially harsh sentence that awaits a recalcitrant holdout. If the other keeps silent, then one can obtain the favorable treatment accorded a state’s witness by confessing. Thus, confession is the dominant strategy (see game theory) for each. But when both confess, the outcome is worse for both than when both keep silent. The concept of the prisoners’ dilemma was developed by RAND Corporation scientists Merrill Flood and Melvin Dresher and was formalized by Albert W. Tucker, a Princeton mathematician.

The prisoners’ dilemma has applications to economics and business. Consider two firms, say Coca-Cola and Pepsi, selling similar products. Each must decide on a pricing strategy. They best exploit their joint market power when both charge a high price; each makes a profit of ten million dollars per month. If one sets a competitive low price, it wins a lot of customers away from the rival. Suppose its profit rises to twelve million dollars, and that of the rival falls to seven million. If both set low prices, the profit of each is nine million dollars. Here, the low-price strategy is akin to the prisoner’s confession, and the high-price akin to keeping silent. Call the former cheating, and the latter cooperation. Then cheating is each firm’s dominant strategy, but the result when both “cheat” is worse for each than that of both cooperating.

Arms races between superpowers or local rival nations offer another important example of the dilemma. Both countries are better off when they cooperate and avoid an arms race. Yet the dominant strategy for each is to arm itself heavily.

On a superficial level the prisoners’ dilemma appears to run counter to Adam Smith’s idea of the invisible hand. When each person in the game pursues his private interest, he does not promote the collective interest of the group. But often a group’s cooperation is not in the interests of society as a whole. Collusion to keep prices high, for example, is not in society’s interest because the cost to consumers from collusion is generally more than the increased profit of the firms. Therefore companies that pursue their own self-interest by cheating on collusive agreements often help the rest of society. Similarly, cooperation among prisoners under interrogation makes convictions more difficult for the police to obtain. One must understand the mechanism of cooperation before one can either promote or defeat it in the pursuit of larger policy interests.

Can “prisoners” extricate themselves from the dilemma and sustain cooperation when each has a powerful incentive to cheat? If so, how? The most common path to cooperation arises from repetitions of the game. In the Coke-Pepsi example, one month’s cheating gets the cheater an extra two million dollars. But a switch from mutual cooperation to mutual cheating loses one million dollars. If one month’s cheating is followed by two months’ retaliation, therefore, the result is a wash for the cheater. Any stronger punishment of a cheater would be a clear deterrent.

The following five points elaborate on the idea:

1. The cheater’s reward comes at once, while the loss from punishment lies in the future. If players heavily discount future payoffs, then the loss may be insufficient to deter cheating. Thus, cooperation is harder to sustain among very impatient players (governments, for example).

2. Punishment will not work unless cheating can be detected and punished. Therefore, companies cooperate more when their actions are more easily detected (setting prices, for example) and less when actions are less easily detected (deciding on nonprice attributes of goods, such as repair warranties). Punishment is usually easier to arrange in smaller and closed groups. Thus, industries with few firms and less threat of new entry are more likely to be collusive.

3. Punishment can be made automatic by following strategies like “tit for tat.” This idea was popularized by University of Michigan political scientist Robert Axelrod. Here, you cheat if and only if your rival cheated in the previous round. But if rivals’ innocent actions can be misinterpreted as cheating, then tit for tat runs the risk of setting off successive rounds of unwarranted retaliation.

4. A fixed, finite number of repetitions is logically inadequate to yield cooperation. Both or all players know that cheating is the dominant strategy in the last play. Given this, the same goes for the second-last play, then the third-last, and so on. But in practice we see some cooperation in the early rounds of a fixed set of repetitions. The reason may be either that players do not know the number of rounds for sure, or that they can exploit the possibility of “irrational niceness” to their mutual advantage.

5. Cooperation can also arise if the group has a large leader, who personally stands to lose a lot from outright competition and therefore exercises restraint, even though he knows that other small players will cheat. Saudi Arabia’s role of “swing producer” in the opec cartel is an instance of this.

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To the extent possible under law, Charles Durning Carroll has waived all copyright and related or neighboring rights to A Philosophy Reader, except where otherwise noted.