 The position of humanists on the species-relativity of moral status is uncertain. Given the critical role they assign to “the distinctive form of common life” of human beings for moral recognition and obligation, it is not obvious that Mulhall or Diamond would require an intelligent Martian to recognize and respect the moral status of cognitively normal human beings, let alone of human beings with radical cognitive impairments. Indeed, it is not clear how humans could confidently impute intelligence to Martians if their embodiment was sufficiently different from ours, let alone whether we could regard them as subject to moral obligations of any kind. Similarly, it is not clear whether Mulhall and Diamond would hold that humans were required to treat Martians as moral equals, even if they could attribute intelligence and moral sensitivity to them. The role they assign to distinctively human forms of life raises doubts about the possibility of mutual comprehension, recognition, and respect.