Thought experiments are a key tool of analytic philosophy. They involve considering a real-world or imaginary situation which provokes a powerful moral or evaluative judgement. These judgements can then be used to test whether a philosophical theory is right or wrong, much as scientific experiments are used to test whether scientific theories are true or false. If a philosophical theory and our judgements conflict, then that could count as evidence against the theory.
Not everyone agrees on the validity of evidence gathered using thought experiments. Some argue that, because they abstract away from reality (though, as noted above, they can involve real-world situations), thought experiments ignore the emotions, relationships and every-day experiences that shape our actual decision-making. Yet these things, critics claim, are philosophically relevant. More straightforwardly, what happens if two people respond differently to the same situation? Is one correct and one incorrect, as we would conclude in the case of a scientific experiment?
These are challenging questions. Something it might help to bear in mind is the distinction philosopher Derek Parfit drew between ‘deep’ and ‘merely technical’ impossibility. A situation is deeply impossible if it violates the laws of nature. It is merely technically impossible if, however implausible it may be, it is at least consistent with reality. We should be more wary about the usefulness of our judgements in deeply impossible cases. So much about our existence would be different if the laws of nature did not hold that the validity of our judgements here seems dubious. Moreover, while it is possible for two people to respond differently to a thought experiment, this might simply call for refining the situation until one of them changes their mind.
Thought experiments can also be strange, shocking and funny. They give philosophers a chance to show off qualities – creativity and wit – that logical reasoning does not. We hear below from different members of Philosophy Exchange about the thought experiments they find most interesting and what we can learn from them.
Singer’s ‘Drowning Child’ Case – Rob
Imagine you’re walking through a park one day. You approach a small pond, where you’re surprised to see a small child splashing about. There aren’t any adults supervising the child and, as you get closer, you realise they can’t swim. If you don’t jump in and rescue them, they will probably drown. You’re wearing an expensive pair of shoes, which you will ruin if you jump in. What should you do? It seems only a moral monster could say that you shouldn’t rescue the child. Doing so will bring about great benefits (saving a child’s life) for minimal cost (ruining your shoes). Most people would probably even say you have an obligation to rescue the child. You would be morally blameworthy (even if not legally culpable) if you didn’t. Yet, Peter Singer argues, we in rich countries have the opportunity to save a child’s life, but many of us effectively let them drown. By giving relatively small amounts of money to effective charities operating in poor countries, we could save a child (even many children) from dying from preventable causes, such as malaria.
I like Singer’s ‘Drowning Child’ case because it’s so simple yet so compelling. Most objections to it focus on whether the analogy between saving the child and giving to charities operating in poor countries holds. This is important but, in my view, beside the point. Yes, we should scrutinise whether charities really are effective. But this objection argues for seeking better evidence, not that we don’t have an obligation to save the drowning child. The thought experiment leads to a radical conclusion: that we should do more, much more (perhaps giving 10% of our incomes to effective charities, as Singer proposes), to help the poorest people in the world.
If you’d be interested in reading Singer’s argument for yourself, you can download his book ‘The Life You Can Save’ as a free pdf here.
Descartes’ ‘Evil Genius’ Case – Cedar
René Descartes’ famous statement “I think, therefore I am” is the result of a thought experiment in radical doubt. Descartes sought truth. But he endeavored to doubt all of his beliefs because he figured that if he could find a belief that he could not doubt, then he could use that belief as a foundation upon which to reconstruct the rest of his belief system, this time with increased confidence in its truth.
In order to explore the bounds of possible doubt, Descartes imagined that an evil genius was tricking him into believing everything that he thought he knew about the world. Descartes found it possible to think that all of his beliefs about the external world, such as his beliefs about colors and shapes and sounds, were merely the result of the machinations of such an evil genius. Then, however, Descartes turned his thoughts to his own mind. At this point, Descartes realized that if he is doubting, then he must exist, since he must be doing the doubting. Thus, Descartes concluded that whenever he thinks, he exists. This is a belief that Descartes could not doubt.
I strongly feel the force of this argument. I have done this same thought experiment in my own head, and I find that I can admit the possibility of the external world not existing, but I cannot doubt that I exist. However, Descartes then attempted to build upon this result in order to provide his other beliefs. I find these later arguments less airtight. That said, one reason why I appreciate this thought experiment is that it provides a clear path which others can take. Subject all of your beliefs to criticism, and see how well they can withstand that criticism. Once you do this, you will have a much better sense of the epistemic value of your beliefs.
You can read more about Descartes’ adventures in radical doubt in his ‘Meditations on First Philosophy’, published in 1641, and available in many pdf forms online. See, for instance.
Schrödinger’s Cat – April
Imagine a cat, a flask of poison, and a radioactive source placed in a sealed box. If an internal monitor detects radioactivity (i.e. a single atom decaying), the flask will be shattered and release the poison, killing the cat. Without external disturbance, the cat is considered to be simultaneously alive and dead, a state known as the “quantum superposition”. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. Schrodinger’s Cat is a thought experiment devised by Austrian-Irish physicist Erwin Schrödinger during his discussion with Albert Einstein. It seeks to answer the question of when and why exactly quantum superposition ends.
This seemingly abstruse narrative has much more real-world applications than people expect. Principally, it articulates the problem of measurement. A few months ago, I decided to buy a Fitbit, the smart watch that claims to measure all your vitals, including resting heart rates, sleep quality, blood oxygen level, etc. Like many other health-conscious individuals, I was curious to see how I am doing. A few weeks in, I realised that the watch does much more than quietly monitoring my bodily functions. Seeing my own vitals every single day made me exceptionally aware of the discrepancy between what I hoped them to be and what they actually are, and that simple awareness impacted my vitals. I get anxious when I see my blood oxygen level falls (yes, Covid-19 has made us all paranoid about this very particular standard). The anxiety decreased my sleep quality, which in turn, lowers my blood oxygen level even more. The downward spiral continued till one day I got considerably upset and called my mother, only to hear her laughing on the other end and calling me the “Schrödinger’s Cat”.
I love entertaining myself with Schrödinger’s Cat because it opens my mind up to appreciate that everything in the universe is so interconnected that sometimes even the curiosity of a single human being could alter the reality. It makes me feel so powerful and powerless at the same time: Powerful that I could change the objective by one action; powerless because I cannot control the direction of that change in any sense. The dichotomy that true agency only exists in the face of ultimate uncertainty humbles me.
I stopped using the Fitbit a while ago. I have come to term with the fact that I can never “quietly observe” my own vitals, and instead of inevitably altering them with my curiosity, I’d rather just let them be.
To read more about Schrödinger’s Cat, you could start by reading John Gribbin’s 1985 book, In Search of Schrödinger’s Cat, which explains in layman’s term the logic and implications of the famous thought experiment.