The author of this study undertakes an investigation of the metaethical grounds of ""rights"" theory, with special focus on the controversial issue of whether creatures other than humans can and should be considered true subjects of ""rights"". He contends that before assigning rights to this or that individual or group, whether human or not, we need to be very clear about what it is we are assigning, to whom and why. The book argues that the efforts to build a case supporting animal and environmental ""rights"" fail in their quest, and that any such effort resting on a Darwinian evolutionary base is likewise condemnded to fail. The author investigates life phenomena, followed by a detailed comparative study of knowing, communicating and doing, as these are observed in the human and nonhuman animal. This is followed by an overview of diverse views advanced by contemporary environmental ethnicists and animal ""rights"" advocates, including Peter Singer, Tom Regan, J. Baird Callicott, Laura Westra, and Don E. Marietta Jr. Conclusions drawn from this study include the claims that: classic Darwinian theory provides no admissable premise from which to derive a theory of inherent, inalienable rights; no satisfactory explanation of the origin of rghts and obligation can derive save from within the context of natural law theory; the human person alone unqualifiedly possesses rights; and the view that vegetarianism is an ethical mandate is neither compatible with the Christian world view, nor philosophically sound.