10 variations of the trolley problem to explain the difference between climate action and inaction

Young-jin Choi
13 min readMay 12, 2021


Photo by Jason Blackeye on Unsplash

What is behind climate inactivism?

The climate crisis represents the defining existential challenge of our time. There is reason to believe that a failure to stabilize the anthropogenic global temperature rise at well below 2 degrees C will permanently damage the potential for human progress for millennia to come. Many climate activists thus share the view that the climate crisis implies an ethical duty of historic significance to take determined climate action. Its success must be measured by the extent to which a sufficiently rapid and deep decarbonization of present civilization can be achieved (the #racetozero), followed by enormous volumes of negative global GHG emissions therafter. To this end, transformative climate policies and systemic interventions are urgently needed (nationally as well as interntionally), including consequently enforced regulatory mandates, steep carbon pricing and unprecedented volumes of additional public transformation spending. Establishing these policies and interventions in turn requires a critical mass of committed “climate activists” to create sufficient pressure in the political and pre-political public sphere.

While the level of public awareness and concern about the need for climate action has recently begun to rise significantly, so has seemingly the level of opposition from “climate inactivists”, who prefer to (directly or indirectly) delay and weaken ambitious climate policy proposals. I differentiate this group from climate denialists and skeptics, who (openly or secretly) question the climate science per se se. Instead, I primarily refer to politicians, who have become aware about a genuine need to take climate action but are hesitant yet to support interventions that they deem to be a threat to short-term economic growth and social stability. Instead, they prefer incremental but ultimately insufficient measures, or stay silent/”neutral” on this matter, which (unfortunately) leads to the same outcome as “climate inaction”. What I found puzzling is why so many people are still so hesitant to support more determined climate action, considering the current state of climate science. I wondered how this could be the case, given that many of them are parents or grandparents themselves, who care about the future future of their descendants. After all, they are not necessarily less ethical or less loss averse human beings than climate activists.

Possible explanations: The tragedy of the commons, short-termism, and the trolley problem

I found one possible explanation in the concept of the “tragedy of the commons” popularized by the ecologist Garret Hardin in 1968 and described as as the “tragedy of the horizon” by Mark Carney in the context of the climate crisis. Based on the famous “prisoner’s dilemma”, the “tragedy of the commons” provides a game-theoretical explanation for how rational agents, by prioritizing a narrow and short-sighted concept of self-interest over cooperation, collectively cause a catastrophic outcome that no one wanted to happen. A key factor for a closely related systemic behavioral pattern known as “overshoot and collapse", is a structural misalignment of economic incentives with desirable behaviors owing to externalities/market failure, such as the insufficient pricing of GHG emissions. The tragedy of the commons provides a compelling argument why purely voluntary commitments tend to be insufficient und why international cooperation (as opposed to geopolitical rivalry), aligning economic incentive structures with desired behaviors and and changing the regulatory “rules of the game” (i.e. of the economic and financial system) are so critical.

Another possible explanation is provided by the concept of “long-termism”, which makes a strong ethical case for a duty to protect humanity’s future potential based on intergenerational empathy/utility and humanist values. Long-termism stands in sharp contrast to the currently predominant “short-termism”, which Richard Fisher aptly described as “civilization’s greatest threat”. Yet, I felt that the tragedy of the commons and the present lack of long-termism within political and economic decision makers can only partially explain why human societies — in the face of an existential threat — continue to lack the unity of purpose, the urgency awareness, and the strong political will that is needed for determined climate action.

I believe a more comprehensive explanation can be provided by the well known “trolley problem” and different variations of it. Accordingly, one of the main reasons why “climate inactivists” remain hesitant to support determined climate action — while “climate activists” consider it a historical ethical duty — can be found in different perceptions and assumptions regarding the parameters of the ethical problem that the climate crisis represents: Many climate inactivists seem convinced that inaction is ethically preferable to action. The trolley problem and the variants described in the following can help us understand how exactly their assumptions regarding the ethics of the climate crisis differ. As long as these differences persist, it will be difficult to mobilize broad support for determined climate action.

The basic version of the trolley problem: “the switch”

The trolley problem describes a popular thought experiment about an ethical dilemma that was described by the moral philosopher Philippa Foot in 1967 and has recently become a popular internet meme based on a drawing by Jesse Prinz. In its basic version known as “the switch”, a runaway trolley is assumed to be on course to kill 5 people tied onto the main track ahead. The spectator is standing nearby a switch that could divert the trolley into a side track, where one person is tied onto the track and would be killed. The spectator has only two choices:

  • action: activate the switch, thus letting the death of the person on the side track happen or
  • inaction: refrain from activating the switch, thus letting the death of 5 people happen.

The basic version of the thought experiment serves to illustrate the difference between a consequentialist and a deontologist ethic. On the one hand, the consequentialist ethic favors action, i.e. saving the lives of many people at the cost of the loss of relatively few. On the other hand, according to the deontologist ethic, the negative “duty to do no harm” to another person has a greater ethical weight, thus overriding the positive “duty to rescue”, indepentently from the number of lives that could be saved. It appears that there is no clear ethical solution for this dilemma. Nevertheless, at an individual level, studies have shown that 90% of respondents would intuitively support activating the switch. From a legal perspective, the spectator would likely be charged with homicide for activating the switch, but could argue “necessity” for defence, provided the jurisdiction allowed to do so (not all do). Moreover it is worth noting that in most jurisdictions, there would likely be no legal repercussions to be feared for failing the duty to rescue in this particular case.

Neutral Variations of the trolley problem

The temporal switch

In order to better represent the ethical problem presented by the climate crisis we can add a temporal dimension to the basic version, by assuming that the main track leads through a time portal. On the other side of the portal there are still five people tied to the track but they are located in the future rather than the present. Insofar as the lives of future people are no less worth than the lives of present people, the ethical dilemma is rather similar to the one in “the switch“.

The non-fatal switch

In another variation, the severity of the consequences for the people on the tracks is reduced to non-fatal injuries, e.g. due to the presence of speed bumps. In this case, too, the ethical arguments are comparable to the basic version, although instead of human lives, people’s physical integrity is at stake.

Both the temporal switch and the non-fatal switch represent “neutral” variations of the basic version, i.e. they are neither more nor less in favor of action or inaction. In the following sections I’m going to describe variations of the trolley problem that clearly favor either inaction or action, partly building on the neutral variations.

Variations of the trolley problem favoring inaction

The following four variations of the trolley problem are in favor of inaction over action:

  • the fat man
  • the asymmetric stakes
  • the asymmetric uncertainty
  • the temporal discrimination

The fat man

The deontological argument in favor of inaction becomes stronger in a well-known variation of the trolley problem called “the fat man” developed by the philosopher Judith Thomson in 1976. It differs from the basic version insofar as the trolley can only be stopped by pushing an innocent bystander (with sufficient body mass) onto the main track from a footbridge. In contrast to “the switch” and its neutral variations, the bystander would not only be killed as a result of a direct (rather than indirect) and violent act, but he would be used clearly as a means to the end of stopping the trolley. Many climate inactivists are likely to identify with the innocent bystander as a victim: They don’t recognize their own role in creating this situation, and feel unrelated to the people on the track. Without strong concepts of agency and necessity, they primarily perceive determined climate action as an excessive violation of their “fundamental right” to the unconstrained pursuit of short-term self-interest. They are trapped within the incentive structure that underlies the tragedy of the commons.

The asymmetric stakes

Inaction is further favored when the stakes are assumed to be asymmetrically distributed in a certain way. In this variation, a speed bump on the main track would ensure that the 5 persons are only non-fatally injured while the person on the side track would still be killed. In the context of the climate crisis, many climate inactivists seem to overestimate the (opportunity) costs of determined climate action, while at the same time severely understimating the magnitude of the future damages, losses and risks of climate inaction that are to be avoided. Unfortunately, there is reason to believe that even past economic damage estimates of earlier IPCC reports have likely been unrealistically low. However, this is not only a matter of perception. In the absence of clear incentive structures, those collective damages appear too uncertain, long-term and fragmented to feel relevant at an individual level. Once the most profitable or cost-efficient decarbonization options are exhausted, further investments into decarbonization are perceived to create an inacceptably high economic burden. A “rational“ agent with a mandate to maximize short-term profits cannot voluntarily accept this unless forced by regulatory mandates or by market prices that integrate the social cost of carbon emissions.

The asymmetric uncertainty

Adding uncertainty to the trolley problem represents another way to simulate the perception of an asymmetric distribution of the stakes. In this variation, the death of the person on the side track is considered to be certain, whereas the death of the five people on the main track is uncertain, for example because the number of people on the main track cannot be clearly determined due to limited visibility, or because they are assumed to be standing on the track (instead of being tied to it) or because only one or the first few of them may actually be fatally injured. Corresponding with this variation, climate inactivists may find it difficult to accept the magnitude of the losses and risks of climate inaction as long as they cannot be quantified with certainty at individual levels. In particular, the geopolitical risks of rising global temperatures with regard to armed (nuclear) conflicts over critical resources are difficult to quantify and therefore tend to be underestimated by economists and climate scientists alike.

The temporal discrimination

Based on the “temporal switch” we can imagine a variation in which only one person is tied onto the main track, whereas five people are tied onto the side track. Obviously, inaction would be favorable if this was indeed the situation, but in the context of the climate crisis, it is more likely the case that future lives are being excessively undervalued relative to present lives, e.g.:

  • owing to the salience of the present and the contincency of those who are yet unborn,
  • due to a lack of intergenerational empathy/long-termism,
  • by applying unnecessarily high and static discount rates over long time periods.

Variations of the trolley problem favoring action

The following four variations of the trolley problem favor action over inaction:

  • the driver
  • the person responsible, with remote control and child
  • the deep temporal switch
  • the reverse asymmetric stakes

The driver

It is worth noting that in Foots original version of the trolley problem, the thought experimenter is actually the trolley driver instead of a spectator. This makes a substantial difference from an ethical point of view: Foot correctly argues that the driver actually faces a conflict between two negative duties not to harm other people in this case. Thus, the difference between action and inaction boils down to a tough but necessary choice between a greater and a lesser bad. In the context of the climate crisis, many climate activists identify with the current generation as “the driver” of a human civilization that cannot be stopped, but at least there is still a choice with regard to the trajectory global GHG emissions take as the 21st unfolds.

The person responsible, with remote control and child

In this variation, the person on the side track is actually responsible for the situation. For example, he or she is assumed to have caused the trolley to get ouf of control through negligence, and/or to have tied the 5 people onto the main track earlier. The spectator now would have an additional justice-based argument to favor action over inaction. Moreover, it is assumed that the person tied onto the side track possesses a remote control for the switch, thereby eliminating the need for a spectator. Finally, it is assumed that the 5 people on the main track include a child of the person responsible. In this variation, the deontological argument that a person may not be used as a means becomes less relevant insofar as one is free to use him/herself as a means to an end. At the same time, the person controlling the switch is also the one who would be harmed by activitating it. Narrow self-interest would prevent the person from doing so, inspite of a “duty to rescue” which is supported by his/her responsbility for the situation. But since the 5 people on the main track include the responsible person’s child, it would also be against his/her broader self-interest and ethical integrity to refrain from taking action. The causal responsibility of past and current generations for the climate crisis not only implies an intergenerational duty to avoid existential future damages and risks but also a duty (following the “polluter pays principle”) to indemnify future generations for the damages and losses that could not be avoided.

The deep temporal switch

A closely related variation of “humanity at stake” is the “deep temporal switch” which expands the “temporal switch” variation by replacing the five people on the track with the future of humanity — potentially billions and trillions of future humans. Alternatively, one could imagine that a group of people critical for the continued realization of humanity’s full future potential — e.g. the equivalent to the first (or last remaining) members of the human species — is tied to the main track. In this case, by virtue of the sheer number of (future) lives at stake and their significance for the potential of the human species, the consequentialist argument should arguably be comparatively stronger than the deontological argument.

The reverse asymmetrical stakes

Finally, the stakes can be assumed to be distributed asymmetrically in the opposite way as they are in “the asymmetric stakes” variation. A speed bump on the side track ensures that the person tied onto it would only be non-fatally injured (if at all). In the context of the climate crisis, it can be argued that the costs of determined climate action are relatively small compared to the enormous cumulative losses and risks caused by climate inaction, implying in a huge net gain of welfare. In addition, decarbonization-related activities and investments would create unprecedented amounts of economic value and jobs that could well exceed the costs of determined climate action. This means that in our thought experiment, the person on the side track would actually benefit from activating the switch. Of course, it is apparent that there are some stakeholders would would experience disproportionate economic losses from determined climate action (in particular Petrostates, fossil fuel dependent regions, high-carbon industries, their employees and shareholders etc). It is an important task of organized human societes to address any social hardship and to ensure the transition into a negative emissions economic is not only successful, but also as socially just and as orderly as possible.

Which variation of the trolley problem comes closest to the reality of the climate crisis?

I believe that a combination of all four variations favoring action over inaction, namely “the driver”, “the reverse asymmetrical stakes”, “the person responsible, with remote control and child” and “the deep temporal switch”, comes rather close to represent the ethical dilemma of the climate crisis. Accordingly, the ethical case for determined climate action is overwhelming. Based on this, we can characterize the climate crisis as a neccessity ethical choice which is certainly a tough one, but also one that offers a clear ethical solution. Staying neutral or silent is not an option but favors inaction. In contrast, the ethical dilemma of the climate crisis as it is perceived by climate inactivists is largely based on inadequate assumptions and misinformation, making a poorly justified case for climate inaction. The variations of the trolley problem favoring inaction illustrate that many climate inactivists are not simply driven by mere narrow self-interest (although some probably are) but consider it their ethical duty to delay, weaken or refuse to support determined climate action. The key to converting climate inactivists into climate activists then lies in updating their assumptions so that they become better aligned with the ethical reality of the climate crisis, e.g.

  • by promoting a better understanding of the tragedy of the commons,
  • by fostering long-termism and intergenerational empathy,
  • by clarifying the (reverse) asymmetric distribution of the stakes (including our own children), as well as
  • by emphasizing our generation’s collective responsibility and agency as the “drivers” of the runaway vehicle that is human civilization.