In recent years, nonhuman animals have been at the center of an intense philosophical debate. In particular, many authors have criticized traditional morality, maintaining that the way in which we treat members of other species is ethically indefensible. We routinely use animals as means to our ends—in fact, we treat them in ways in which we would deem it profoundly immoral to treat human being. Though they are "moral patients", that is, beings whose treatment may be subject to moral evaluation—their status is infinitely inferior to ours. Are such double standards warranted? And, if so, on what grounds?
While not being completely overlooked by philosophers, the first justification offered is powerful and widespread at the societal level, mainly due to its simplicity. To the question of what divides us from the other animals, the answer is: the fact that they are not human. On such a view, what makes the difference is the possession, or lack, of a genotype characteristics of the species Homo sapiens. Is this a good reply? No. Those appealing to species membership work within the framework of the human egalitarian paradigm. And it is just the line of reasoning that supports human equality that implies, by denying the moral relevance of race or sex membership, the rejection of the idea that species membership in itself can make a difference in moral status. If one claims that biological characteristic like race and sex cannot play a role in ethics, how can one attribute a role to another biological characteristics such as species membership? Moral views that, while rejecting racism and sexism, accept "speciesism"—the view that grants members of our own species special moral status—are internally inconsistent.
Sheer speciesism is hardly plausible. But there are more sophisticated ways of defending our current double standards to which the theoretical defenders of the status quo tend to turn. For most philosophers, it is not species membership rather than the possession of rationality that plays a central role. We can set aside for the sake of argument the (questionable) assumption that rationality is a human prerogative in order to focus on the moral significance attached to rationality.
Though many other defences of the doctrine of human superiority have been put forward, the appeal to species membership, the appeal to the possession of rationality, as a precondition of morals, and the appeal to this very same characteristic as a means to intersubjective agreement are certainly the most basic, around which all the others revolve. If none of them can justify maintaining nonhuman animals in their present inferior moral condition, it seems plausible to infer that our current attitude is deeply flawed.