  This proposal has the attractive feature that it treats evenhandedly members of the human species and members of any other species of being there might be anywhere in the universe. If any beings possess rational agency capacity at a threshold level, they are persons and have the moral worth and dignity that attaches to persons. The proposal also provides an attractive approach to the issue of what rights and duties humans and other animals have with respect to each other. The proposal suggests that the more it is the case that an individual being attains some degree of rational agency capacity, below the threshold of full personhood, the more morally considerable that being is.