This article explores Peter Singer’s Animal Liberation thesis and examines the arguments against his work, particularly from certain moral philosophers in the late 1970s and 1980s who seriously engaged with his ideas. This article argues that due to the straightforward, minimalist nature of Singer’s preference utilitarianism, his arguments have remained highly defensible and persuasive. By advancing sentience, above characteristics like intelligence or rationality, as a sufficient criterion for possessing interests, Singer provides a justifiable principle for morally considering animal interests equal (...) to those of humans. Numerous moral philosophers have challenged Singer, but they have struggled to seriously counter his core principle and to resolve the argument of ‘marginal cases’—that is, why do infants and intellectually disabled humans have moral status and animals do not. Ultimately, Singer broadly challenged prevailing anthropocentric views of animals and, in some instances, persuaded some of his most intransigent opponents. (shrink)

Human–nonhuman chimeras have been the focus of ethical controversies for more than a decade, yet some related issues remain unaddressed. For example, little has been said about the relationship between the origin of transferred cells and the morally relevant capacities to which they may give rise. Consider, for example, a developing mouse fetus that receives a brain stem cell transplant from a human and another that receives a brain stem cell transplant from a dolphin. If both chimeras acquire morally relevant (...) capacities as a result of transplantation, and if those capacities are indistinguishable, should the difference in cell origin matter to how we classify these creatures? I argue that if morally relevant capacities are easy to detect, cell origin is irrelevant to how the chimera ought to be treated. However, if such capacities are hard to detect, cell origin should play a role in considerations about how to treat the chimera. (shrink)