Here is a question that I've had to simplify and idealise to the point that it no longer corresponds exactly to any real-world situation. However, I think it still captures a very important and topical moral question:
Consider a group of economic (im)migrants who wish to enter your country (i.e. they're not escaping persecution or war, they're just seeking a better life). If you accept them then there is no measurable (e.g. economic) benefit to your country. Nevertheless, you are both able and willing to accommodate them. However, suppose it is known that a percentage P of them will have some attribute A that you perceive to be negative (e.g. criminal, Islamist, racist, welfare migrant). What is the highest P that you would be willing to tolerate (above which you would decline entry to the entire group)?
I think most people (with some notable exceptions) would agree that:
- If P is no greater than the probability native to the host country then it is acceptable
- If P is close to 100% then it is unacceptable
So, for most people, there is some vague threshold above which they would not be willing to accept the group. Of course, this threshold would depend on the nature of A. For instance, you probably wouldn't care if 10% could not speak your language, whereas if 10% were rapists then you would think twice. This threshold matters, so how should we rationally decide what is acceptable?
I realise that there are intelligent people on all sides of this debate and so I'm not expecting a direct answer to the question posed. Instead, I'm looking for guidance on how to tackle this question. Are there analogies and thought experiments that can help simplify or reframe this problem? Are there any moral frameworks that provide solutions? Have any notable philosophers written on this issue? How should I, as a citizen who ultimately gets to vote on such matters, make a decision?