As Harry Brighouse mentioned at CT, I’m sceptical of the value of artificial “thought experiments” in moral philosophy, without having a fully coherent basis for this scepticism. One thing I don’t like about the term “thought experiment” is the implication that the results of such thought experiments constitute data, and therefore that an ethical theory is more satisfactory if it fits such data than if it does not. The way I’d prefer to approach such problems involves an iterative loop, with repeated stages of (i) consider reasonable general principles (ii) compare to intuitions about specific cases (iii) where appropriate, adjust judgements on specific cases (iv) revise general principles to give a better fit to adjusted intuitions. That is, I don’t think either general principles or specific intuitions are trumps.
I thought I’d throw some examples into the mix that might tempt some other CTers such as Kieran into the fray. Harry mentioned the Thomson violinist example as a thought experiment that clarifies reasoning about abortion and obligations to others. As I said, I prefer to avoid such implausible hypotheticals. That leads me to suggest looking at some related non-hypothetical choices.
As a real-life alternative to the violinist question, I’m interested question of whether there are circumstances under which it is morally obligatory to donate blood, or organs, in order to save the lives of others. And, if it is morally obligatory, is the obligation one that can justifiably be enforced by law? For what it’s worth, I think the answer to the first question is “Yes” and to the second is “Probably not”. But a positive answer to the first question would seem to justify a “presumed consent” answer to the second, as applied to organ donation after death (that is, people should be presumed to have consented to organ donation unless they explicitly opt out). Of course, that raises the question of whether such a presumption can be made effectual and whether it would in fact raise donation rates, issues on which Kieran has written quite a bit.
Answers to these questions do not translate directly into answers to the corresponding questions about issues like abortion or foreign aid. But they seem to me likely to give more insight than thought experiments about violinists. And, even if you do want to go hypothetical, it would seem to me to be preferable to stick as closely as possible to reality. For example, to go from a general responsibility to a specific responsibility, consider the following case that is only mildly hypothetical. Consider an organ transplant/blood donation technology that can be applied anywhere but is time-sensitive, so that, in the event of a car crash it must be used at the scene. In the case of a crash where someone is injured through the fault of another, should the person at fault be compelled to donate blood/organs to save the life of the innocent party?