Arguing by analogy in the fetal tissue debate

In the debate over fetal tissue use, an analogy is often drawn between removing organs from the body of a person who has been murdered to use for transplantation, and collecting tissue from an aborted fetus to use for the same purpose. The murder victim analogy is taken by its proponents to show that even if abortion is the moral equivalent of murder, there is still no good reason to refrain from using the fetal tissue, since as a society we do not see any problem about using organs from murder victims. However, I argue that the analogy between murder victims and aborted fetuses does not hold -- the two situations are not the same in all morally relevant respects. Thus the murder victim analogy does not provide an argument in favour of fetal tissue transplant. In conclusion, I point to some of the potential pitfalls of using analogies in ethical argument.