I want to argue for the importance of the notion human being in ethics. Part I of the paper presents two different sorts of argument against treating that notion as important in ethics. A. Here is an example of the first sort of argument. What makes us human beings is that we have certain properties, but these properties, making us members of a certain biological species, have no moral relevance. If, on the other hand, we define being human in terms (...) which are not tied to biological classification, if we treat as the properties which make us human the capacities for reasoning or for self-consciousness, then indeed those capacities may be morally relevant, but if they are morally significant at all, they are significant whether they are the properties of a being who is a member of our species or not. And so it would be better to use a word like ‘person’ to mean a being that has these properties , to bring out the fact that not all human beings have them and that non-human beings conceivably might have them. (shrink)