He writes that, because the moral rights of humans are based on their possession of certain cognitive abilities, and because these abilities are also possessed by at least some nonhuman animals, such animals must have the same moral rights as humans.
Han mener, at eftersom menneskers rettigheder er baseret på besiddelsen af bestemte, kognitive evner, og eftersom i det mindste nogle ikke-menneskelige dyr også besidder disse evner, bør sådanne dyr have de samme rettigheder som mennesker.