Many debates in arenas such as bioethics turn on questions regarding the moral status of human beings at various stages of biological development or decline. It is often argued that a human being possesses a fundamental and inviolable moral status insofar as she is a “person”; yet, it is contested whether all or only human beings count as persons. Perhaps there are non-human person, and perhaps not every human being satisfies the definitional criteria for being a person. A further question, which will be the primary focus of this paper, concerns what essential features of personhood endow persons, human or otherwise, with their moral status and the inherent rights they concomitantly possess. A survey of the history of philosophical theorizi...