As members of the most evolutionarily developed species on earth, most of us share the common-sensical belief that our treatment of animals should be based more or less on moral grounds. However, it is also an undeniable fact that for more than two millennia, from the appearance of the first moral theories in Ancient Greece until almost the last quarter of the 20th century, this traditional moral concern for animals has gone hand in hand with their systematic exclusion from the (...) moral community of human beings, which deprives them of basic protective rights against moral abuse and mistreatment. A radical paradigm shift in ethics emerges, especially in the last quarter of the 20th century, when some philosophers begin to question this anthropocentric conception of ethics and the “otherness” of animals in terms of their traditional location outside the ethical discourse. Peter Singer, who is a utilitarian, and Tom Regan, who defends the “rights view” against Singer’s utilitarianism, are two prominent representatives of this new ethical approach. After showing how Singer and Regan reject speciesism, this paper focuses on Regan’s critique of Singer’s account and adds new objections that show that utilitarianism has serious general defects even if it is restricted to human beings. Moreover, these defects give rise to more complicated problems when utilitarianism is applied to animals. After pointing to some weak aspects in Regan’s theory, the paper spells out the sketch of an alternative account that points to the possibility of a synthesis of utility principle and right principle. Accordingly, Regan’s worse-off principle deduced from the rights view is interpreted as a formal principle, while the utility principle as the material content of it is accepted: as long as there is no violation of the worse-off principle, one ought to deduce particular commands to maximize utility for specific cases out of the application of the utility principle. In this context, the worse-off principle has only a negative and formal function that prevents the utility principle from overriding individual rights by giving it its obligatory form. (shrink)