Historically, Western philosophy relegated animals to the status of automatons or property (Descartes, 1637). The 19th century saw the first modern animal welfare laws, such as the UK’s Cruel Treatment of Cattle Act (1822), targeting overt brutality. However, the late 20th century witnessed a philosophical rupture with the publication of Peter Singer’s Animal Liberation (1975)—grounded in utilitarianism—and Tom Regan’s The Case for Animal Rights (1983)—grounded in deontological rights theory. This paper distinguishes these two schools, arguing that understanding their tension is essential for effective advocacy and policy formation.

Singer does not invoke “rights” per se but argues for equal consideration of interests . Since animals have an interest in avoiding pain, their suffering must be weighed equally with human suffering. While Singer is a utilitarian (seeking to minimize total pain), his logic leads to a radical conclusion: most animal use (especially factory farming) cannot be justified because the pleasure humans derive from cheap meat does not outweigh the immense suffering inflicted.