Reframing the ethical issues in part-human animal research: the unbearable ontology of inexorable moral confusion.

Research that involves the creation of animals with human-derived parts opens the door to potentially valuable scientific and therapeutic advances, yet invokes unsettling moral questions. Critics and champions alike stand to gain from clear identification and careful consideration of the strongest ethical objections to this research. A prevailing objection argues that crossing the human/nonhuman species boundary introduces inexorable moral confusion (IMC) that warrants a restriction to this research on precautionary grounds.