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)