A common objection against the use of thought experiments, whether they be in ethics, metaphysics or science, is that they are only imaginary. That they are not of the real world. That they are completely distant from the world that we understand. A. Walsh (2010) calls this objection to thought experiments as “objection from modality”. This objection is that we cannot apply the imagined cases to moral questions because they are so ‘modally bizarre’ or ‘distant from the world as we know it’. Walsh explains that in cases where we are making cases about general moral principles, the distinction between real and imagined cases are irrelevant, where he says (2010):
“While applied ethics deals with ‘real world’ cases, if an argument regarding such a case relies centrally on a general moral principle, then it is warranted to test its generality against a range of possible scenarios, which may or may not be modally bizarre.”
To assist in Walsh’s point. I will give an example of a moral general principle that ‘we are always morally obligated to obey the law’. In my primary school ethics classes, I have used the example of Rosa Parks to prompt discussion among the students about whether we are always morally obligated to obey the law. However, some will argue that considering Rosa Parks is a real example, thus distinct from thought experiments that involve imagined situations. But consider this thought experiment:
Imagine a world just like our own. However, there never existed segregation based on skin colour. There never was a civil rights movement in the US. No bus boycott. No Rosa Parks. No MLK Jr. After all, there was never a need for a civil rights movement. In this world, two philosophers are discussing whether we are always morally obligated to obey the law. One of the philosophers comes up with this thought experiment: “Imagine a world where African Americans must, by law, sit at the back of the bus or stand when a white person needs the seat. In this world, an African American woman refuses to leave her seat for a white woman, thus breaking the law”.
In our world, this is not imaginary. In a discussion about obeying the law, all we need to ask is: “Did Rosa Parks do the wrong thing when she broke the law?”. However, in the other world it is an imagined situation, but nonetheless has the same event with the same question (that anticipates an answer that refutes the proposition “we are always morally obligated to obey the law”). So, in this case there appears to be no relevant differences between the real case and the imagined case. I argue that since there are no apparent relevant differences, appealing to the real or imaginary aspects of a thought experiment says nothing about their legitimacy.
Walsh, A. (2010). A moderate defence of the use of thought experiments. Ethical theory and moral practice. 14(1). 467-481.