" In sum, reliance on cognitive characteristics beyond sentience to justify the use of nonhumans in experiments requires either that we assume that these characteristics are morally relevant or that we ignore the fact that we do not regard the lack of such characteristics as morally relevant where humans are concerned. We are left with one and only one reason to explain our differential treatment of animals: We are human and they are not, and species difference alone justifies differential treatment. But this criterion is entirely arbitrary and no different from maintaining that, although there is no special characteristic possessed only by whites, or no defect possessed by blacks that is not also possessed by whites, we may treat blacks as inferior to whites merely on the basis of race. It is also no different from saying that, although there is no special characteristic possessed only by men or no defect possessed only by women, we may treat women as inferior to men based merely on sex. "

― Gary L. Francione , Animals as Persons: Essays on the Abolition of Animal Exploitation