Argument: Animals cannot possess rights because they have no moral judgement
Tibor R. Machan. "We Are Not What We Eat. Putting Humans First: Why We Are Nature’s Favorite". Rowman & Littlefield, 2004. xvi + 135 pgs. - "Only those capable of deliberation and choice can have rights, since a right by definition designates an area in which someone has free jurisdiction. Unless you have the capacity to reason, how can anything be up to you to decide? "The most fundamental objection to the notion that animals have rights is that only human beings have the requisite moral nature for ascribing to them basic rights. However closely humans and lower animals resemble each other, human beings alone possess the capacity for free choice and the responsibility to act ethically" (p. 10)."
Carl Cohen. "Why animals have no rights. The Case for the Use of Animals in Biomedical Research" The New England Journal of Medicine 315, no. 14 (October 2,1986): 865-69 - "The attributes of human beings from which this moral capability arises have been described variously by philosophers, both ancient and modern: the inner consciousness of a free will (Saint Augustine); the grasp, by human reason, of the binding character of moral law (Saint Thomas); the self-conscious participation of human beings in an objective ethical order (Hegel); human membership in an organic moral community (Bradley); the development of the human self through the consciousness of other moral selves (Mead); and the underivative, intuitive cognition of the rightness of an action (Prichard). Most influential has been Immanuel Kant's emphasis on the universal human possession of a uniquely moral will and the autonomy its use entails. Humans confront choices that are purely moral; humans -- but certainly not dogs or mice -- lay down moral laws, for others and for themselves. Human beings are self-legislative, morally auto-nomous [sic]. [p.865-866]
Animals (that is, nonhuman animals, the ordinary sense of that word) lack this capacity for free moral judgment. They are not beings of a kind capable of exercising or responding to moral claims. Animals therefore have no rights, and they can have none. This is the core of the argument about the alleged rights of animals. The holders of rights must have the capacity to comprehend rules of duty, governing all including themselves. In applying such rules, the holders of rights must recognize possible conflicts between what is in their own interest and what is just. Only in a community of beings capable of self-restricting moral judgments can the concept of a right be correctly invoked.
Humans have such moral capabilities. They are in this sense self-legislative, are members of communities governed by moral rules, and do possess rights. Animals do not have such moral capacities. They are not morally self-legislative, cannot possibly be members of a truly moral community, and therefore cannot possess rights. In conducting research on animal subjects, therefore, we do not violate their rights, because they have none to violate.
[...]This criticism misses the central point. lt is not the ability to communicate or to reason, or dependence on one another, or care for the young, or the exhibition of preference, or any such behavior that marks the critical divide. Analogies between human families and those of monkeys, or between human communities and those of wolves, and the like, are entirely beside the point. Patterns of conduct are not at issue. Animals do indeed exhibit remarkable behavior at times. Conditioning, fear, instinct, and intelligence all contribute to species survival. Membership in a community of moral agents nevertheless remains impossible for them. Actors subject to moral judgment must be capable of grasping the generality of an ethical premise in a practical syllogism. Humans act immorally often enough, but only they -- never wolves or monkeys -- can discern, by applying some moral rule to the facts of a case, that a given act ought or ought not to be performed. The moral restraints imposed by humans on themselves are thus highly abstract and are often in conflict with the self-interest of the agent. Communal behavior among animals, even when most intelligent and most endearing, does not approach autonomous morality in this fundamental sense. [p.866-867]
Genuinely moral acts have an internal as well as an external dimension. Thus, in law, an act can be criminal only when the guilty deed, the actus reus, is done with a guilty mind, mens rea. No animal can ever commit a crime; bringing animals to criminal trial is the mark of primitive ignorance. The claims of moral right are similarly inapplicable to them. Does a lion have a right to eat a baby zebra? Does a baby zebra have a right not to be eaten? Such questions, mistakenly invoking the concept of right where it does not belong, do not make good sense. Those who condemn biomedical research because it violates "animal rights" commit the same blunder." [p. 867]"