In this paper I present a new objection to the Aristotelian Naturalism defended by Philippa Foot. I describe this objection as a membership objection because it reveals the fact that AN invites counterexamples when pressed to identify the individuals bound by its normative claims. I present three examples of agents for whom the norms generated by AN are not obviously authoritative: mutants, aliens, and the Great Red Dragon. Those who continue to advocate for Foot's view can give compelling replies to (...) the first two of these examples, but their replies drive the view into an unwelcome result when it faces the last example. I conclude that the concept of being human, on which AN crucially depends, is not as straightforward as Foot's advocates presume. (shrink)