by Russell Newton

The Runaway Trolley

A prime example of mulling around solutions and perspectives for which a million variables exist is the Trolley Problem. Would you rather allow one person to die or five? This is a classic thought experiment that forces you into a series of escalating moral dilemmas. It makes you consider who you are, and what you value, and why that is. In the end, nothing is solved or clarified, except your own thoughts. There is no answer except to systematically learn and explore.

The Problem of the Runaway Trolley

Consider a seemingly simple hypothetical situation: you are standing and watching a train that’s headed right for five people tied to the tracks, who will certainly be killed if the train continues. If you pull a lever, the train will divert and head down another track, killing instead just a single person tied to that track. So, if you fail to act, five people die, but if you do act, only one person dies. The question is, would you pull the lever? Why?
Now, the idea is not to say, “That would never happen, so who cares?” The situation, obviously, is contrived. But it forces us to think outside the box and take a closer look at our default mental models. It invites us to have a conversation beyond what is immediately and concretely in front of us.
Simply by asking the question, you have participated in one of philosophy’s classic thought experiments, the so-called Trolley Problem. You may be spurred to think all kinds of new thoughts, strengthening different modes of reasoning just as an athlete trains different muscles of their body:
You may wonder, if we think a single life is important, does it imply that five lives are five times as important? Here you’re grappling with utilitarianism. You may believe most people would act to minimize harm if given the chance, considering what you know of how people normally behave (deductive reasoning), or you may wonder if not acting in this case completely absolves a person of guilt (now you’re thinking about moral philosophy).
You may wonder, what if the single person was your child or parent? What if you had to physically push a person in front of the train to stop it? What if each of the five people had cancer and was going to die within the next year? What if there were five babies, yet the lone person standing was akin to Albert Einstein or some other genius? What if you had the power to sacrifice yourself in their places? What plea would you make if you were the single person? Now you’re practicing switching perspectives and views.
If you ask yourself whether saving a family member versus a stranger is any more ethical, you’re actively seeking and evaluating support for this argument. You might think the whole situation over and decide that it’s implicitly OK to do wrong if it prevents a larger wrong from occurring. Congratulations—you’ve made a hypothesis. You could “test” this hypothesis (not an opinion) by asking whether pulling the lever should result in being punished by the law. You could make a prediction about what would happen if this was actually the case, in the real world, and on and on…


As you can see, one hypothetical situation can stimulate a whole new world of critical thinking, in every direction.
In fact, people have been chewing over the trolley problem for years, teasing apart what it can tell us about how we think about culpability, the value of human life, moral behavior and psychology, the limits of a utilitarian approach in philosophy, and more. Many variants have been dreamt up too—for example, what if the single person was a villain?
While such thought experiments might seem glib—and perhaps a little unsettling—they do serve a useful purpose. They are used by philosophers to investigate what beliefs we hold to be true and, as a result, what kind of knowledge we can have about ourselves and the world around us. Sometimes, that process will be a little bizarre or unpleasant. But sometimes, it can also push us beyond our limits and open up new and different perspectives.
Long story short, thought experiments teach us to think.


In the chapters that follow, we’ll delve into famous thought experiments that have been carried out throughout history, and their surprising ramifications. We’ll look at ancient and modern philosophers alike, as well as physicists and great thinkers from all over the world. Many classical thought experiments have had profound effects on the way we think about ourselves in the modern world, so at the very least, learning about what each one implies will give you a richer insight into mankind’s philosophical development through the ages.

The Zombie Cat

Let’s begin with the famous but often-misunderstood thought experiment of Schrodinger’s cat. To understand the point that physicist Erwin Schrodinger was trying to make, we need to know a little about the state of theoretical physics at the time, including the Copenhagen Interpretation. Niels Bohr and Werner Heisenberg were proponents of this interpretation of quantum mechanics in the 1920s, and used it to explain and conceptualize some strange results found in quantum mechanics experiments. Under this interpretation, physical systems demonstrate what’s called “wave function collapse,” which simply means that their properties are only definite once measured—and quantum mechanics can only show us the probabilities of a certain outcome. Importantly, the Copenhagen Interpretation is only one of many interpretations of quantum theory, each with their own support and criticisms, of which Schrodinger’s cat is also only one.


The thought experiment goes like this: imagine there is a cat placed inside a box for an hour. Inside the box is a Geiger counter (which can measure radioactive particles), a small container of radioactive material, a hammer and a little vial of cyanide that will kill the cat if broken.
The radioactive material is set up in such a way as to allow for a 50 percent chance that after the hour has passed, a single atom of the material will decay (it’s not important to understand radioactive decay, only that radioactive elements are unstable and liable to emit particles, i.e. radioactivity). The setup is such that if a particle is emitted, the Geiger counter records it and the hammer drops, breaking the vial and killing the cat.
Schrodinger argued that, using the Copenhagen Interpretation, you could say that the cat is literally both dead and alive before you open the box to confirm the case. In other words, it exists in some strange state where it is simultaneously living and deceased, and only opening the box collapses the uncertainty.
If this sounds kind of weird to you, that’s the point. Schrodinger used this thought experiment to highlight how uncertainty at the subatomic level could have strange implications for bigger objects—like cats. This thought experiment forms just a small part of a large and complex conversation in theoretical physics, and is beyond the scope of this book. However, even without understanding the details, one can see why the experiment has been so useful.


In this branch of physics, measurement of phenomena itself was under question—so normal experimentation was out of the question. When trying to understand things like probability distributions, whether light is a particle or a wave, what constitutes measurement and so on, we have to resort to thought experiments.
Schrodinger thus used a purely hypothetical situation in lieu of a real-world experiment to make his point. He took a premise from an accepted model and asked, “What happens if we think this way for large objects?” This scenario, like the Trolley Problem, has inspired many subsequent thought experiments. Indeed, much of theoretical physics plays out in this abstract, purely mathematical space, far outside the lab.
What can this thought experiment teach the layperson about critical thinking? Often, the flaws in our arguments or beliefs can be found if we merely follow our own models to their full conclusion. In other words, we use thought experiments to fully consider all the implications of our perspective—i.e., if such-and-such is the case, what does it mean for everything else? In Schrodinger’s case, the sheer implausibility of the outcome was an implied criticism. In considering any argument or point of view, ask yourself: How would the world have to be if my theory were true? Is the world that way? What does my argument imply? Are the implications desirable/logical/true? And if not, does it invalidate my original argument?


This might appear to epitomize one of the loudest criticisms of philosophy, that it is a bunch of circuitous thinking with no real ending or purpose. However, this endless analysis and prodding of your thoughts is the real purpose in enriching yourself.