Various debates in bioethics have been focused on whether non-persons, such as marginal humans or non-human animals, deserve respectful treatment. It has been argued that, where we cannot agree on whether these individuals have moral status, we might agree that they have symbolic value and ascribe to them moral value in virtue of their symbolic significance. In the paper I resist the suggestion that symbolic value is relevant to ethical disputes in which the respect for individuals with no intrinsic moral (...) value is in conflict with the interests of individuals with intrinsic moral value. I then turn to moral status and discuss the suitability of personhood as a criterion. There some desiderata for a criterion for moral status: it should be applicable on the basis of our current scientific knowledge; it should have a solid ethical justification; and it should be in line with some of our moral intuitions and social practices. Although it highlights an important connection between the possession of some psychological properties and eligibility for moral status, the criterion of personhood does not meet the desiderata above. I suggest that all intentional systems should be credited with moral status in virtue of having preferences and interests that are relevant to their well-being. (shrink)

The rare condition known as dicephalus occurs when (prior to implantation) a zygote fails to divide completely, resulting in twins who are conjoined below the neck. Human dicephalic twins look like a two-headed person, with each brain supporting a distinct mental life. Jeff McMahan has recently argued that, because they instance two of us but only one animal, dicephalic twins provide a counterexample to the animalist's claim that each of us is identical with a human animal. To the contrary, I (...) argue that in cases of dicephalus it is obvious neither that there is one animal nor that there are two of us. Consequently, the animalist criterion does not straightforwardly apply to cases of dicephalus. I defend an account of dicephalus that is both sensitive to the complexity of twinning phenomena and not inconsistent with animalism. In my view, dicephalic twins are a borderline case of the concept HUMAN ANIMAL. I conclude with some speculative remarks concerning the normative import (if any) of my claim that dicephalic twins are a borderline case. (shrink)