  Potentially more confusing would be an individual that was clearly a non-person but who had just enough human material that they could not be definitively classified as human or as non-human; for example, a blastocyst-stage chimpanzee embryo which has had half of its inner cell mass replaced with hESCs. But even in this extreme case, those who believe that a fully-human conceptus has no moral status prior to the onset of consciousness will simply conclude that a blastocyst-stage chimeric conceptus has no moral status either. Those who believe that a fully human conceptus has full moral status from conception would need to decide how to classify such a chimera and may be confused by the situation. But it is unclear why Robert and Baylis think that someone’s being confused about the specific case of the chimera would also make them revisit their general belief that being a human being is sufficient for full moral status. If the clear lack of personhood of a human embryo or fetus does not cause such people to revisit the general issue, why would the clear lack of personhood of a chimeric embryo, which would seem to have even less going for it from this perspective, cause them to revisit it? Indeed, it is not clear why borderline cases pose any challenge to a general belief about necessary and sufficient conditions. Someone who believes that being a male sibling is necessary and sufficient for being a brother will not be led to doubt that biconditional by the existence of an intersex person who is on the border between being male and being female. To the extent that it is vague whether the individual is male, it is also vague whether the individual is a brother.