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 theorizing on what it means to be a person yields a broad consensus upon the key capacities being rational thought, self-consciousness, and autonomous volition. It is not sufficient, however, simply to cite these capacities, but to explain why these particular capacities bear moral import. A more recent concern has developed regarding the possible future existence of so-called “post-persons” who, due to their enhanced cognitive and emotive capacities, may be morally superior to mere persons and thereby possess a higher moral status. This paper will conclude with an analysis of the extent to which this concern is warranted. (shrink)