As philosophy comes to occupy more and more of the public’s attention—which is good news—it is not surprising that a lot of that attention is directed at ideas and examples that are dramatic and easy to describe. Chief among these, it seems, is the trolley problem (it it has even shown up on a network sitcom). The trolley problem is so popular, though, that discussion of it, like the trolley itself, seems out of control. So I thought that a very brief primer, directed mainly at journalists and other non-specialists, would be of use.

The particular prompt for this post is yet another popular press article about the so-called shortcomings of trolley-style thought experiments, this time by Daniel Engber at Slate. He discusses a lab experiment which purported to show that “people’s thoughts about imaginary trolleys and other sacrificial hypotheticals did not predict their actions.” He calls this a “discomfiting” result. But it’s only discomfiting if you are making some mistakes about what these types of examples are. I hope that the following is of use in helping to keep writing about the trolley problem on the right track.

*******

Trolley Problems: A Brief Caution

Please note that the value of trolley problems and the like does not depend on:

Whether the trolley problem is realistic, that is, whether trolley systems are engineered to avoid these kinds of problems, whether one is very unlikely to encounter any trolleys in one’s life, whether one is unlikely to be confronted with a situation in which they must quickly choose between options in which different numbers of people die

Whether what people in simulations or experiments actually choose to do in trolley-like situations matches with what they say they would do in such situations

Which parts of people’s brains show increased activity when they choose one option or another

The idea that what one thinks one should do in such problems tells us straightforwardly what one should do in various real life situations

But, you might ask, if trolley problems are not realistic, or predictive, or a means by which science can solve moral problems, or action-guiding, then what value do they have? Their value is in raising questions and problems for our moral thinking, such as:

whether the numbers of people being harmed or benefited matter to what we should do, and if so, why?

whether there is a distinction worth making between acting and not acting, and if so, whether that distinction makes a difference to the value of resultant benefits and harms, and if so, why?

whether there is a distinction worth making between what an agent intends and what an agent merely foresees, and if so, whether that distinction makes a difference to the value of resultant benefits and harms, and if so, why?

Each of these produces more questions: what is a harm or benefit? What is it to harm or benefit? How do good and bad add up across persons? What is an action? What is an intention? What is the relationship between metaphysics and ethics? And so on.

Here are some mistakes people make using the trolley problem:

Using “trolley problem” to refer to the question of what one would do in one example. Among philosophers, today, the name “trolley problem” refers to the apparently conflicting judgments that arise from two different trolley examples.

Thinking that the central question these examples are about is: “What would you do?” That is a psychology question. More closely related to what philosophers are up to are the questions: “What should you do?” and “why?” But even those are not the main question. The main question is: what problems does this thought experiment and our answers to these questions raise for our understanding of morality?

Thinking that we can easily extract from our responses to the trolley problem more general principles or justified responses to real-world choices. This is false because, first, the trolley problems are just one type of possible obstacle to systematic, coherent moral thinking—there are many others. Second, the real world is not artificially constrained in its options nor epistemically transparent, as the examples are.

None of this is to say that trolley problems cannot be legitimately critiqued—they have been and will continue to be. It’s just to caution against some simplistic and wrong-headed types of criticism.

Comments welcome.