Animal Liberation Now

Animal Liberation Now is an updated edition of philosopher Peter Singer's Animal Liberation, originally published in 1975. Singer renews the book's core argument while incorporating new scientific evidence about animal cognition and addressing the environmental consequences of animal agriculture.

Singer opens by establishing his central ethical principle: The principle of equal consideration of interests requires that the interests of all sentient beings receive equal moral weight, regardless of species. He traces this idea through ethical thinkers including Jeremy Bentham, John Stuart Mill, and John Rawls, noting that few extended moral impartiality to nonhuman animals. Singer defines "speciesism," a term coined by philosopher Richard Ryder, as a prejudice favoring the interests of one's own species, and draws an explicit parallel with racism and sexism. The capacity for suffering, he argues, is the only defensible boundary for moral consideration. He cites the 2012 Cambridge Declaration on Consciousness, which confirmed that mammals, birds, and many other creatures possess the neurological substrates that generate consciousness, and reviews evidence for pain in fish and invertebrates. A 2021 scientific review found strong evidence of sentience in cephalopod mollusks, such as octopuses, and decapod crustaceans, such as crabs and lobsters, leading to their inclusion in the UK Animal Welfare (Sentience) Act of 2022. Singer then announces the book's two central case studies: animal experimentation and factory farming.

Singer estimates that approximately 200 million animals are used in experiments worldwide each year and notes that U.S. law excludes rats, mice, and birds from regulatory oversight. He documents experiments that inflict severe suffering without producing significant human benefits, beginning with psychologist Harry Harlow's maternal deprivation experiments at the National Primate Research Center in Madison, Wisconsin, in the late 1950s, in which infant monkeys were raised in bare wire cages and isolated in stainless steel chambers. In the 1970s, Harlow and his student Stephen Suomi escalated the research with devices such as "monster mothers" that ejected compressed air or sharp brass spikes. Suomi continued similar work for three decades until the National Institutes of Health closed his laboratory in 2015. Singer identifies a fundamental dilemma: Either animal minds are unlike human minds, making such experiments unlikely to benefit humans, or they are similar enough to make the experiments morally objectionable. He details "learned helplessness" research, in which dogs were subjected to inescapable electric shocks, and notes that researcher Steven Maier acknowledged in 1984 that the model was probably not useful for understanding human depression, yet similar experiments continued. Singer recounts the history of toxicity testing, including the LD50 test, which determines the lethal dose for 50 percent of test animals, and the Draize test, which involves placing substances in rabbits' eyes. He credits civil rights activist Henry Spira with launching a successful 1980s campaign against Revlon that led cosmetics companies to fund alternatives, though these tests have not been fully eliminated. He cites research showing that 85 percent of biomedical research is wasted and proposes a guideline: An experiment on animals cannot be justified unless using a profoundly brain-damaged human would also be justified, though he acknowledges some experiments may meet this standard.

Singer then turns to factory farming. He opens with Iowa Select Farms, where in 2020, veterinarians killed 243,016 pigs by sealing them in barns and raising the temperature above 130°F until the pigs stopped squealing. The process, triggered by slaughterhouse closures during the COVID-19 pandemic, exceeded two and a half hours in at least one case. More than 83 billion birds and mammals are slaughtered for food globally each year. Singer describes broiler chickens confined in windowless sheds at densities as low as half a square foot per bird, bred to grow so rapidly that many develop chronic leg pain. In the egg industry, approximately 300 million male chicks are killed annually in the United States, and 65 percent of laying hens remain in battery cages smaller than the space a bird physically occupies. He traces the European Union's campaign against battery cages, culminating in a 2021 commitment to ban all cages for farmed animals by 2027, and contrasts this with slower progress in the United States. He documents conditions for pigs, 75 percent of whose breeding sows are kept in stalls too small to turn around, and examines the veal and dairy industries. He also addresses fish, noting that 787 billion to 2.3 trillion wild-caught fish are killed annually, many by slow suffocation, alongside an estimated 124 billion farmed fish.

Singer argues that individuals should adopt plant-based diets, presenting the boycott of factory-farmed products as directly proportional in its impact to participation. He refutes the claim that factory farms are necessary to feed the world, noting that beef converts only 2.9 percent of the calories it consumes into food for humans and that replacing all animal products in the U.S. diet with plant-based alternatives would free enough land to feed an additional 350 million people. He cites the Intergovernmental Panel on Climate Change (IPCC) finding that diets low in meat and dairy are associated with lower greenhouse gas emissions. He evaluates "conscientious omnivores" who eat humanely raised animal products, acknowledging philosophical difficulty in refuting their position but arguing that truly humane commercial production is rare. Singer draws the line for ethical consumption: Strong evidence supports sentience in vertebrates, octopuses, and decapod crustaceans, while oysters and marine mussels, which attach to fixed surfaces, are unlikely to feel pain.

Singer traces the intellectual history of speciesism in Western thought, from the Genesis account of human dominion through the ancient Greek philosopher Aristotle's claim that animals exist for human use, to Christianity's exclusion of animals from moral concern. He notes that the medieval theologian Thomas Aquinas argued cruelty to animals is wrong only insofar as it may lead to cruelty toward humans. Singer credits the 17th-century philosopher René Descartes with the most extreme position: that animals are mere automata without consciousness, a view that provided cover for vivisectors who nailed dogs to boards and dismissed their cries as mechanical noise. He traces reform through the Enlightenment, contrasting the philosopher Immanuel Kant's view that animals are merely means to human ends with Bentham's question "Can they suffer?" and the passage of the first anti-cruelty law in Britain in 1822. He argues that the naturalist Charles Darwin's theory of evolution should have transformed humanity's treatment of animals but that the ideology of human supremacy proved resistant to scientific evidence. He documents recent shifts in Catholic teaching, including Pope Francis's 2015 encyclical Laudato si', which rejects "the notion that our being created in God's image and given dominion over the earth justifies absolute domination over other creatures" (241).

In the final chapter, Singer addresses common objections and assesses the animal movement's progress. He refutes the "humans come first" objection by noting its circularity and that leaders against racism and sexism, from the British abolitionist William Wilberforce to early American feminists, have also championed animal welfare. He presents research on "motivated mind perception," showing that people told they would soon eat meat subsequently denied mental characteristics to the animal they expected to eat. He documents victories since 1975, including the European Union's phaseout of battery cages, veal stalls, and sow stalls; bans on fur farming; and the end of invasive research on great apes. Corporate commitments increased the proportion of cage-free hens in the United States from 3 percent in 2005 to 35 percent in 2022. Singer discusses the growth of plant-based alternatives and investment in cultivated meat—grown from animal cells without breeding, raising, or killing animals—which he views as potentially decisive in ending factory farming. He concludes by acknowledging that despite all progress, more animals suffer in laboratories and factory farms than ever before, and that the outcome depends on whether humans will prove capable of ending their exploitation of other species not because they are forced to, but because they recognize their position as morally indefensible.