Animal rights is the idea in which some, or all, non-human animals are entitled to the possession of their own existence and that their most basic interests—such as the need to avoid suffering—should be afforded the same consideration as similar interests of human beings.^[3]

Its advocates oppose the assignment of moral value and fundamental protections on the basis of species membership alone—an idea known since 1970 as speciesism, when the term was coined by Richard D. Ryder—arguing that it is a prejudice as irrational as any other.^[4] They maintain that animals should no longer be viewed as property or used as food, clothing, research subjects, entertainment, or beasts of burden.^[5] Multiple cultural traditions around the world such as Jainism, Taoism, Hinduism, Buddhism and Animism also espouse some forms of animal rights.

In parallel to the debate about moral rights, animal law is now widely taught in law schools in North America, and several prominent legal scholars support the extension of basic legal rights and personhood to at least some animals. The animals most often considered in arguments for personhood are bonobos and chimpanzees. This is supported by some animal rights academics because it would break through the species barrier, but opposed by others because it predicates moral value on mental complexity, rather than on sentience alone.^[6]

Critics of animal rights argue that nonhuman animals are unable to enter into a social contract, and thus cannot be possessors of rights, a view summed up by the philosopher Roger Scruton, who writes that only humans have duties, and therefore only humans have rights.^[7] Another argument, associated with the utilitarian tradition, is that animals may be used as resources so long as there is no unnecessary suffering;^[8] they may have some moral standing, but they are inferior in status to human beings, and any interests they have may be overridden, though what counts as "necessary" suffering or a legitimate sacrifice of interests varies considerably.^[9] Certain forms of animal rights activism, such as the destruction of fur farms and animal laboratories by the Animal Liberation Front, have also attracted criticism, including from within the animal rights movement itself,^[10] as well as prompted reaction from the U.S. Congress with the enactment of laws allowing these activities to be prosecuted as terrorism, including the Animal Enterprise Terrorism Act.^[11]

Aristotle argued that animals lacked reason (logos), and placed humans at the top of the natural world, yet the respect for animals in ancient Greece was very high. Some animals were considered divine, e.g. dolphins. In the Book of Genesis 1:26 (5th or 6th century BCE), Adam is given "dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth." Dominion need not entail property rights, but it has been interpreted, by some, over the centuries to imply ownership.^[13]

Contemporary philosopher Bernard Rollin writes that "dominion does not entail or allow abuse any more than does dominion a parent enjoys over a child."^[14] Rollin further states that the Biblical Sabbath requirement promulgated in the Ten Commandments "required that animals be granted a day of rest along with humans. Correlatively, the Bible forbids 'plowing with an ox and an ass together' (Deut. 22:10–11). According to the rabbinical tradition, this prohibition stems from the hardship that an ass would suffer by being compelled to keep up with an ox, which is, of course, far more powerful. Similarly, one finds the prohibition against 'muzzling an ox when it treads out the grain' (Deut. 25:4–5), and even an environmental prohibition against destroying trees when besieging a city (Deut. 20:19–20). These ancient regulations, virtually forgotten, bespeak of an eloquent awareness of the status of animals as ends in themselves", a point also corroborated by Norm Phelps.^[14][15]

The philosopher and mathematician Pythagoras (c. 580–c. 500 BCE) urged respect for animals, believing that human and nonhuman souls were reincarnated from human to animal, and vice versa.^[16] Against this, Aristotle (384–322 BCE), student to the philosopher Plato, argued that nonhuman animals had no interests of their own, ranking them far below humans in the Great Chain of Being. He was the first to create a taxonomy of animals; he perceived some similarities between humans and other species, but argued for the most part that animals lacked reason (logos), reasoning (logismos), thought (dianoia, nous), and belief (doxa).^[12]

Theophrastus (c. 371 – c. 287 BCE), one of Aristotle's pupils, argued that animals also had reasoning (logismos) and opposed eating meat on the grounds that it robbed them of life and was therefore unjust.^[17][18] Theophrastus did not prevail; Richard Sorabji writes that current attitudes to animals can be traced to the heirs of the Western Christian tradition selecting the hierarchy that Aristotle sought to preserve.^[12]

Plutarch (1 C. CE) in his Life of Cato the Elder comments that while law and justice are applicable strictly to men only, beneficence and charity towards beasts is characteristic of a gentle heart. This is intended as a correction and advance over the merely utilitarian treatment of animals and slaves by Cato himself.^[19]

Tom Beauchamp (2011) writes that the most extensive account in antiquity of how animals should be treated was written by the Neoplatonist philosopher Porphyry (234–c. 305 CE), in his On Abstinence from Animal Food, and On Abstinence from Killing Animals.^[20]

According to Richard D. Ryder, the first known animal protection legislation in Europe was passed in Ireland in 1635. It prohibited pulling wool off sheep, and the attaching of ploughs to horses' tails, referring to "the cruelty used to beasts."^[21] In 1641, the first legal code to protect domestic animals in North America was passed by the Massachusetts Bay Colony.^[22] The colony's constitution was based on The Body of Liberties by the Reverend Nathaniel Ward (1578–1652), an English lawyer, Puritan clergyman, and University of Cambridge graduate. Ward's list of "rites" included rite 92: "No man shall exercise any Tirrany or Crueltie toward any brute Creature which are usually kept for man's use." Historian Roderick Nash (1989) writes that, at the height of René Descartes' influence in Europe—and his view that animals were simply automata—it is significant that the New Englanders created a law that implied animals were not unfeeling machines.^[23]

The Puritans passed animal protection legislation in England too. Kathleen Kete writes that animal welfare laws were passed in 1654 as part of the ordinances of the Protectorate—the government under Oliver Cromwell (1599–1658), which lasted from 1653 to 1659, following the English Civil War. Cromwell disliked blood sports, which included cockfighting, cock throwing, dog fighting, bull baiting and bull running, said to tenderize the meat. These could be seen in villages and fairgrounds, and became associated with idleness, drunkenness, and gambling. Kete writes that the Puritans interpreted the biblical dominion of man over animals to mean responsible stewardship, rather than ownership. The opposition to blood sports became part of what was seen as Puritan interference in people's lives, and the animal protection laws were overturned during the Restoration, when Charles II was returned to the throne in 1660.^[24]

The great influence of the 17th century was the French philosopher René Descartes (1596–1650), whose Meditations (1641) informed attitudes about animals well into the 20th century.^[26] Writing during the scientific revolution, Descartes proposed a mechanistic theory of the universe, the aim of which was to show that the world could be mapped out without allusion to subjective experience.^[27]

His mechanistic approach was extended to the issue of animal consciousness. Mind, for Descartes, was a thing apart from the physical universe, a separate substance, linking human beings to the mind of God. The nonhuman, on the other hand, were for Descartes nothing but complex automata, with no souls, minds, or reason.^[26]

Against Descartes, the British philosopher John Locke (1632–1704) argued, in Some Thoughts Concerning Education (1693), that animals did have feelings, and that unnecessary cruelty toward them was morally wrong, but that the right not to be harmed adhered either to the animal's owner, or to the human being who was being damaged by being cruel. Discussing the importance of preventing children from tormenting animals, he wrote: "For the custom of tormenting and killing of beasts will, by degrees, harden their minds even towards men."^[29]

Locke's position echoed that of Thomas Aquinas (1225–1274). Paul Waldau writes that the argument can be found at 1 Corinthians (9:9–10), when Paul asks: "Is it for oxen that God is concerned? Does he not speak entirely for our sake? It was written for our sake." Christian philosophers interpreted this to mean that humans had no direct duty to nonhuman animals, but had a duty only to protect them from the effects of engaging in cruelty.^[30]

The German philosopher Immanuel Kant (1724–1804), following Aquinas, opposed the idea that humans have direct duties toward nonhumans. For Kant, cruelty to animals was wrong only because it was bad for humankind. He argued in 1785 that "cruelty to animals is contrary to man's duty to himself, because it deadens in him the feeling of sympathy for their sufferings, and thus a natural tendency that is very useful to morality in relation to other human beings is weakened."^[31]

Jean-Jacques Rousseau (1712–1778) argued in Discourse on Inequality (1754) for the inclusion of animals in natural law on the grounds of sentience: "By this method also we put an end to the time-honored disputes concerning the participation of animals in natural law: for it is clear that, being destitute of intelligence and liberty, they cannot recognize that law; as they partake, however, in some measure of our nature, in consequence of the sensibility with which they are endowed, they ought to partake of natural right; so that mankind is subjected to a kind of obligation even toward the brutes. It appears, in fact, that if I am bound to do no injury to my fellow-creatures, this is less because they are rational than because they are sentient beings: and this quality, being common both to men and beasts, ought to entitle the latter at least to the privilege of not being wantonly ill-treated by the former."^[32]

In his treatise on education, Emile, or On Education (1762), he encouraged parents to raise their children on a vegetarian diet. He believed that the food of the culture a child was raised eating, played an important role in the character and disposition they would develop as adults. "For however one tries to explain the practice, it is certain that great meat-eaters are usually more cruel and ferocious than other men. This has been recognized at all times and in all places. The English are noted for their cruelty while the Gaures are the gentlest of men. All savages are cruel, and it is not their customs that tend in this direction; their cruelty is the result of their food."

Four years later, one of the founders of modern utilitarianism, the English philosopher Jeremy Bentham (1748–1832), although opposed to the concept of natural rights, argued that it was the ability to suffer that should be the benchmark of how we treat other beings. Bentham claims that the capacity for suffering gives the right to equal consideration; equal consideration is that the interests of any being affected by an action are to be considered and have the equal interest of any other being. If rationality were the criterion, he argued, many humans, including infants and the disabled, would also have to be treated as though they were things.^[34] He did not conclude that humans and nonhumans had equal moral significance, but argued that the latter's interests should be taken into account. He wrote in 1789, just as African slaves were being freed by the French:

The 19th century saw an explosion of interest in animal protection, particularly in England. Debbie Legge and Simon Brooman write that the educated classes became concerned about attitudes toward the old, the needy, children, and the insane, and that this concern was extended to nonhumans. Before the 19th century, there had been prosecutions for poor treatment of animals, but only because of the damage to the animal as property. In 1793, for example, John Cornish was found not guilty of maiming a horse after pulling the animal's tongue out; the judge ruled that Cornish could be found guilty only if there was evidence of malice toward the owner.^[36]

From 1800 onwards, there were several attempts in England to introduce animal protection legislation. The first was a bill against bull baiting, introduced in April 1800 by a Scottish MP, Sir William Pulteney (1729–1805). It was opposed inter alia on the grounds that it was anti-working class, and was defeated by two votes. Another attempt was made in 1802, this time opposed by the Secretary at War, William Windham (1750–1810), who said the Bill was supported by Methodists and Jacobins who wished to "destroy the Old English character, by the abolition of all rural sports."^[37]

In 1809, Lord Erskine (1750-1823) introduced a bill to protect cattle and horses from malicious wounding, wanton cruelty, and beating. He told the House of Lords that animals had protection only as property: "The animals themselves are without protection--the law regards them not substantively--they have no rights!"^[38] Erskine in his parliamentary speech combined the vocabulary of animal rights and trusteeship with a theological appeal included in the Bill's preamble to opposing cruelty.^[39] The Bill was passed by the Lords, but was opposed in the Commons by Windham, who said it would be used against the "lower orders" when the real culprits would be their employers.^[37]

In 1821, the Treatment of Horses bill was introduced by Colonel Richard Martin (1754–1834), MP for Galway in Ireland, but it was lost among laughter in the House of Commons that the next thing would be rights for asses, dogs, and cats.^[41] Nicknamed "Humanity Dick" by George IV, Martin finally succeeded in 1822 with his "Ill Treatment of Horses and Cattle Bill"—or "Martin's Act", as it became known—which was the world's first major piece of animal protection legislation. It was given royal assent on June 22 that year as An Act to prevent the cruel and improper Treatment of Cattle, and made it an offence, punishable by fines up to five pounds or two months imprisonment, to "beat, abuse, or ill-treat any horse, mare, gelding, mule, ass, ox, cow, heifer, steer, sheep or other cattle."^[36]

Legge and Brooman argue that the success of the Bill lay in the personality of "Humanity Dick", who was able to shrug off the ridicule from the House of Commons, and whose sense of humour managed to capture the House's attention.^[36] It was Martin himself who brought the first prosecution under the Act, when he had Bill Burns, a costermonger—a street seller of fruit—arrested for beating a donkey, and paraded the animal's injuries before a reportedly astonished court. Burns was fined, and newspapers and music halls were full of jokes about how Martin had relied on the testimony of a donkey.^[42]

Other countries followed suit in passing legislation or making decisions that favoured animals. In 1822, the courts in New York ruled that wanton cruelty to animals was a misdemeanor at common law.^[22] In France in 1850, Jacques Philippe Delmas de Grammont succeeded in having the Loi Grammont passed, outlawing cruelty against domestic animals, and leading to years of arguments about whether bulls could be classed as domestic in order to ban bullfighting.^[43] The state of Washington followed in 1859, New York in 1866, California in 1868, and Florida in 1889.^[44] In England, a series of amendments extended the reach of the 1822 Act, which became the Cruelty to Animals Act 1835, outlawing cockfighting, baiting, and dog fighting, followed by another amendment in 1849, and again in 1876.

Richard Martin soon realized that magistrates did not take the Martin Act seriously, and that it was not being reliably enforced. Martin's Act was supported by various social reformers who were not parliamentarians and an informal network had gathered around the efforts of Reverend Arthur Broome (1779-1837) to create a voluntary organisation that would promote kindness toward animals. Broome canvassed opinions in letters that were published or summarised in various periodicals in 1821.^[45] After the passage of Richard Martin's anti-cruelty to cattle bill in 1822, Broome attempted to form a Society for the Prevention of Cruelty to Animals that would bring together the patronage of persons who were of social rank and committed to social reforms. Broome did organise and chair a meeting of sympathisers in November 1822 where it was agreed that a Society should be created and at which Broome was named its Secretary but the attempt was short-lived.^[46] In 1824, Broome arranged a new meeting in Old Slaughter's Coffee House in St Martin's Lane, a London café frequented by artists and actors. The group met on June 16, 1824, and included a number of MPs: Richard Martin, Sir James Mackintosh (1765–1832), Sir Thomas Buxton (1786–1845), William Wilberforce (1759–1833), and Sir James Graham (1792–1861), who had been an MP, and who became one again in 1826.^[40]

They decided to form a "Society instituted for the purpose of preventing cruelty to animals"; the Society for the Prevention of Cruelty to Animals, as it became known. It determined to send men to inspect slaughterhouses, Smithfield Market, where livestock had been sold since the 10th century, and to look into the treatment of horses by coachmen.^[40] The Society became the Royal Society in 1840, when it was granted a royal charter by Queen Victoria, herself strongly opposed to vivisection.^[47]

From 1824 onwards, several books were published, analyzing animal rights issues, rather than protection alone. Lewis Gompertz (1783/4–1865), one of the men who attended the first meeting of the SPCA, published Moral Inquiries on the Situation of Man and of Brutes (1824), arguing that every living creature, human and nonhuman, has more right to the use of its own body than anyone else has to use it, and that our duty to promote happiness applies equally to all beings. Edward Nicholson (1849–1912), head of the Bodleian Library at the University of Oxford, argued in Rights of an Animal (1879) that animals have the same natural right to life and liberty that human beings do, disregarding Descartes' mechanistic view—or what he called the "Neo-Cartesian snake"—that they lack consciousness.^[48] Other writers of the time who explored whether animals might have natural (or moral) rights were Edward Payson Evans (1831–1917), John Muir (1838–1914), and J. Howard Moore (1862–1916), an American zoologist and author of The Universal Kinship (1906) and The New Ethics (1907).^[49]

The development in England of the concept of animal rights was strongly supported by the German philosopher Arthur Schopenhauer (1788–1860). He wrote that Europeans were "awakening more and more to a sense that beasts have rights, in proportion as the strange notion is being gradually overcome and outgrown, that the animal kingdom came into existence solely for the benefit and pleasure of man."^[51]

He stopped short of advocating vegetarianism, arguing that, so long as an animal's death was quick, men would suffer more by not eating meat than animals would suffer by being eaten.^[52] Schopenhauer also theorized that the reason people succumbed to the "unnatural diet" of meat-eating was because of the unnatural, cold climate they emigrated to and the necessity of meat for survival in such a climate, for fruits and vegetables could not be dependably cultivated at those times.^[53] He applauded the animal protection movement in England—"To the honor, then, of the English, be it said that they are the first people who have, in downright earnest, extended the protecting arm of the law to animals."^[51] He also argued against the dominant Kantian idea that animal cruelty is wrong only insofar as it brutalizes humans:

The English poet and dramatist Percy Bysshe Shelley (1792–1822) wrote two essays advocating a vegetarian diet, for ethical and health reasons: A Vindication of Natural Diet (1813) and On the Vegetable System of Diet (1829, posth.).

Isabella Beeton (1836-1865) the English reporter, editor and author of "Mrs Beeton's Book of Household Management" was an early advocate against force-fed poultry and caged hens. About the former, she wrote that force-feeding, was a process that "may produce a handsome-looking bird, and it may weigh enough to satisfy the whim or avarice of its stuffer; but, when before the fire, it will reveal the cruel treatment to which it has been subjected, and will weep a drippingpan-ful of fat tears. You will never find heart enough to place such a grief-worn guest at the head of your table". About the necessity for free-range rather than caged hens, she wrote, "We are no advocates for converting the domestic fowl into a cage-bird. We have known amateur fowl-keepers...coop up a male bird and three or four hens in an ordinary egg-chest placed on its side, and with the front closely barred with iron hooping! This system will not do. Every animal, from man himself to the guinea-pig, must have what is vulgarly, but truly, known as “elbow-room;” and it must be self-evident how emphatically this rule applies to winged animals. It may be urged, in the case of domestic fowls, that from constant disuse, and from clipping and plucking, and other sorts of maltreatment, their wings can hardly be regarded as instruments of flight; we maintain, however, that you may pluck a fowl’s wing-joints as bare as a pumpkin, but you will not erase from his memory that he is a fowl, and that his proper sphere is the open air. If he likewise reflects that he is an ill-used fowl — a prison-bird — he will then come to the conclusion, that there is not the least use, under such circumstances, for his existence; and you must admit that the decision is only logical and natural".^[54]

John Stuart Mill (1806–1873), the English philosopher, also argued that utilitarianism must take animals into account, writing in 1864: "Nothing is more natural to human beings, nor, up to a certain point in cultivation, more universal, than to estimate the pleasures and pains of others as deserving of regard exactly in proportion to their likeness to ourselves. ... Granted that any practice causes more pain to animals than it gives pleasure to man; is that practice moral or immoral? And if, exactly in proportion as human beings raise their heads out of the slough of selfishness, they do not with one voice answer 'immoral,' let the morality of the principle of utility be for ever condemned."^[55]

James Rachels writes that Charles Darwin's (1809–1882) On the Origin of Species (1859)—which presented the theory of evolution by natural selection—revolutionized the way humans viewed their relationship with other species. Not only did human beings have a direct kinship with other animals, but the latter had social, mental and moral lives too, Darwin argued.^[56] He wrote in his Notebooks (1837): "Animals – whom we have made our slaves we do not like to consider our equals. – Do not slave holders wish to make the black man other kind?"^[57] Later, in The Descent of Man (1871), he argued that "There is no fundamental difference between man and the higher mammals in their mental faculties", attributing to animals the power of reason, decision making, memory, sympathy, and imagination.^[56]

Rachels writes that Darwin noted the moral implications of the cognitive similarities, arguing that "humanity to the lower animals" was one of the "noblest virtues with which man is endowed." He was strongly opposed to any kind of cruelty to animals, including setting traps. He wrote in a letter that he supported vivisection for "real investigations on physiology; but not for mere damnable and detestable curiosity. It is a subject which makes me sick with horror ..." In 1875, he testified before a Royal Commission on Vivisection, lobbying for a bill to protect both the animals used in vivisection, and the study of physiology. Rachels writes that the animal rights advocates of the day, such as Frances Power Cobbe, did not see Darwin as an ally.^[56]

An early proposal for legal rights for animals came from a group of citizens in Ashtabula County, Ohio. Around 1844, the group proposed an amendment to the U.S. Constitution stating that if slaves from slave states were receiving representation as 3/5 of a person on the basis that they were animal property, all the animal property of the free states should receive representation also.^[58]

The first animal protection group in the United States, the American Society for the Prevention of Cruelty to Animals (ASPCA), was founded by Henry Bergh in April 1866. Bergh had been appointed by President Abraham Lincoln to a diplomatic post in Russia, and had been disturbed by the mistreatment of animals he witnessed there. He consulted with the president of the RSPCA in London, and returned to the United States to speak out against bullfights, cockfights, and the beating of horses. He created a "Declaration of the Rights of Animals", and in 1866 persuaded the New York state legislature to pass anti-cruelty legislation and to grant the ASPCA the authority to enforce it.^[59]

In 1875, the Irish social reformer Frances Power Cobbe (1822–1904) founded the Society for the Protection of Animals Liable to Vivisection, the world's first organization opposed to animal research, which became the National Anti-Vivisection Society. In 1880, the English feminist Anna Kingsford (1846–1888) became one of the first English women to graduate in medicine, after studying for her degree in Paris, and the only student at the time to do so without having experimented on animals. She published The Perfect Way in Diet (1881), advocating vegetarianism, and in the same year founded the Food Reform Society. She was also vocal in her opposition to experimentation on animals.^[60] In 1898, Cobbe set up the British Union for the Abolition of Vivisection, with which she campaigned against the use of dogs in research, coming close to success with the 1919 Dogs (Protection) Bill, which almost became law.

Ryder writes that, as the interest in animal protection grew in the late 1890s, attitudes toward animals among scientists began to harden. They embraced the idea that what they saw as anthropomorphism—the attribution of human qualities to nonhumans—was unscientific. Animals had to be approached as physiological entities only, as Ivan Pavlov wrote in 1927, "without any need to resort to fantastic speculations as to the existence of any possible subjective states." It was a position that hearkened back to Descartes in the 17th century, that nonhumans were purely mechanical, with no rationality and perhaps even no consciousness.^[61]

Avoiding utilitarianism, Friedrich Nietzsche (1844–1900) found other reasons to defend animals. He argued that "The sight of blind suffering is the spring of the deepest emotion."^[62] He once wrote: "For man is the cruelest animal. At tragedies, bull-fights, and crucifixions hath he hitherto been happiest on earth; and when he invented his hell, behold, that was his heaven on earth."^[63] Throughout his writings, he speaks of the human being as an animal.^[64]

In 1894, Henry Salt (1851–1939), a former master at Eton, who had set up the Humanitarian League to lobby for a ban on hunting the year before, published Animals' Rights: Considered in Relation to Social Progress.^[65] He wrote that the object of the essay was to "set the principle of animals' rights on a consistent and intelligible footing."^[66] Concessions to the demands for jus animalium had been made grudgingly to date, he wrote, with an eye on the interests of animals qua property, rather than as rights bearers:

He argued that there was no point in claiming rights for animals if those rights were subordinated to human desire, and took issue with the idea that the life of a human might have more moral worth. "[The] notion of the life of an animal having 'no moral purpose,' belongs to a class of ideas which cannot possibly be accepted by the advanced humanitarian thought of the present day—it is a purely arbitrary assumption, at variance with our best instincts, at variance with our best science, and absolutely fatal (if the subject be clearly thought out) to any full realization of animals' rights. If we are ever going to do justice to the lower races, we must get rid of the antiquated notion of a 'great gulf' fixed between them and mankind, and must recognize the common bond of humanity that unites all living beings in one universal brotherhood."^[66]

In 1902, Lizzy Lind af Hageby (1878–1963), a Swedish feminist, and a friend, Lisa Shartau, traveled to England to study medicine at the London School of Medicine for Women, intending to learn enough to become authoritative anti-vivisection campaigners. In the course of their studies, they witnessed several animal experiments, and published the details as The Shambles of Science: Extracts from the Diary of Two Students of Physiology (1903). Their allegations included that they had seen a brown terrier dog dissected while conscious, which prompted angry denials from the researcher, William Bayliss, and his colleagues. After Stephen Coleridge of the National Anti-Vivisection Society accused Bayliss of having violated the Cruelty to Animals Act 1876, Bayliss sued and won, convincing a court that the animal had been anesthetized as required by the Act.^[67]

In response, anti-vivisection campaigners commissioned a statue of the dog to be erected in Battersea Park in 1906, with the plaque: "Men and Women of England, how long shall these Things be?" The statue caused uproar among medical students, leading to frequent vandalism of the statue and the need for a 24-hour police guard. The affair culminated in riots in 1907 when 1,000 medical students clashed with police, suffragettes and trade unionists in Trafalgar Square. Battersea Council removed the statue from the park under cover of darkness two years later.^[67]

Coral Lansbury (1985) and Hilda Kean (1998) write that the significance of the affair lay in the relationships that formed in support of the "Brown Dog Done to Death", which became a symbol of the oppression the women's suffrage movement felt at the hands of the male political and medical establishment. Kean argues that both sides saw themselves as heirs to the future. The students saw the women and trade unionists as representatives of anti-science sentimentality, while the women saw themselves as progressive, with the students and their teachers belonging to a previous age.^[68]

Members of the English Vegetarian Society who avoided the use of eggs and animal milk in the 19th and early 20th century were known as strict vegetarians. The International Vegetarian Union cites an article informing readers of alternatives to shoe leather in the Vegetarian Society's magazine in 1851 as evidence of the existence of a group that sought to avoid animal products entirely. There was increasing unease within the Society from the start of the 20th century onwards with regards to egg and milk consumption, and in 1923 its magazine wrote that the "ideal position for vegetarians is [complete] abstinence from animal products."^[69]

Mahatma Gandhi (1869–1948) argued in 1931 before a meeting of the Society in London that vegetarianism should be pursued in the interests of animals, and not only as a human health issue. He met both Henry Salt and Anna Kingsford, and read Salt's A Plea for Vegetarianism (1880). Salt wrote in the pamphlet that "a Vegetarian is still regarded, in ordinary society, as little better than a madman."^[69] In 1944, several members, led by Donald Watson (1910–2016), decided to break from the Vegetarian Society over the issue of egg and milk use. Watson coined the term "vegan" for those whose diet included no animal products, and they formed the British Vegan Society on November 1 that year.^[70]

On coming to power in January 1933, the Nazi Party passed a comprehensive set of animal protection laws. The laws were similar to those that already existed in England, though more detailed and with severe penalties for breaking them. Arnold Arluke and Boria Sax write that the Nazis tried to abolish the distinction between humans and animals, to the point where many people were regarded as less valuable than animals.^[71]

In April 1933 they passed laws regulating the slaughter of animals; one of their targets was kosher slaughter. In November the Tierschutzgesetz, or animal protection law, was introduced, with Adolf Hitler announcing an end to animal cruelty: "Im neuen Reich darf es keine Tierquälerei mehr geben." ("In the new Reich, no more animal cruelty will be allowed.") It was followed in July 1934 by the Reichsjagdgesetz, prohibiting hunting; in July 1935 by the Naturschutzgesetz, environmental legislation; in November 1937 by a law regulating animal transport in cars; and in September 1938 by a similar law dealing with animals on trains.^[72] Hitler was a vegetarian in the later years of his life; several members of his inner circle, including Rudolf Hess, Joseph Goebbels, and Heinrich Himmler, adopted some form of vegetarianism, though by most accounts their vegetarianism was not as strict as Hitler's.^[73]

Despite the proliferation of animal protection legislation, animals still had no legal rights. Debbie Legge writes that existing legislation was very much tied to the idea of human interests, whether protecting human sensibilities by outlawing cruelty, or protecting property rights by making sure animals were not harmed. The over-exploitation of fishing stocks, for example, is viewed as harming the environment for people; the hunting of animals to extinction means that humans in the future will derive no enjoyment from them; poaching results in financial loss to the owner, and so on.^[44]

Notwithstanding the interest in animal welfare of the previous century, the situation for animals arguably deteriorated in the 20th century, particularly after the Second World War. This was in part because of the increase in the numbers used in animal research—300 in the UK in 1875, 19,084 in 1903, and 2.8 million in 2005 (50–100 million worldwide), and a modern annual estimated range of 10 million to upwards of 100 million in the US^[74]—but mostly because of the industrialization of farming, which saw billions of animals raised and killed for food on a scale considered impossible before the war.^[75]

In the early 1960s in England, support for animal rights began to coalesce around the issue of blood sports, particularly hunting deer, foxes, and otters using dogs, an aristocratic and middle-class English practice, stoutly defended in the name of protecting rural traditions. The psychologist Richard D. Ryder – who became involved with the animal rights movement in the late 1960s – writes that the new chair of the League Against Cruel Sports tried in 1963 to steer it away from confronting members of the hunt, which triggered the formation that year of a direct action breakaway group, the Hunt Saboteurs Association. This was set up by a journalist, John Prestige, who had witnessed a pregnant deer being chased into a village and killed by the Devon and Somerset Staghounds. The practice of sabotaging hunts (for example, by misleading the dogs with scents or horns) spread throughout south-east England, particularly around university towns, leading to violent confrontations when the huntsmen attacked the "sabs".^[76]

The controversy spread to the RSPCA, which had arguably grown away from its radical roots to become a conservative group with charity status and royal patronage. It had failed to speak out against hunting, and indeed counted huntsmen among its members. As with the League Against Cruel Sports, this position gave rise to a splinter group, the RSPCA Reform Group, which sought to radicalize the organization, leading to chaotic meetings of the group's ruling Council, and successful (though short-lived) efforts to change it from within by electing to the Council members who would argue from an animal rights perspective, and force the RSPCA to address issues such as hunting, factory farming, and animal experimentation. Ryder himself was elected to the Council in 1971, and served as its chair from 1977 to 1979.^[76]

The same period saw writers and academics begin to speak out again in favor of animal rights. Ruth Harrison published Animal Machines (1964), an influential critique of factory farming, and on October 10, 1965, the novelist Brigid Brophy had an article, "The Rights of Animals", published in The Sunday Times.^[61] She wrote:

Robert Garner writes that Harrison's book and Brophy's article led to an explosion of interest in the relationship between humans and nonhumans.^[77] In particular, Brophy's article was discovered in or around 1969 by a group of postgraduate philosophy students at the University of Oxford, Roslind and Stanley Godlovitch (husband and wife from Canada), John Harris, and David Wood, now known as the Oxford Group. They decided to put together a symposium to discuss the theory of animal rights.^[61]

Around the same time, Richard Ryder wrote several letters to The Daily Telegraph criticizing animal experimentation, based on incidents he had witnessed in laboratories. The letters, published in April and May 1969, were seen by Brigid Brophy, who put Ryder in touch with the Godlovitches and Harris. Ryder also started distributing pamphlets in Oxford protesting against experiments on animals; it was in one of these pamphlets in 1970 that he coined the term "speciesism" to describe the exclusion of nonhuman animals from the protections offered to humans.^[78] He subsequently became a contributor to the Godlovitches' symposium, as did Harrison and Brophy, and it was published in 1971 as Animals, Men and Morals: An Inquiry into the Maltreatment of Non-humans.^[79]

In 1970, over lunch in Oxford with fellow student Richard Keshen, a vegetarian, Australian philosopher Peter Singer came to believe that, by eating animals, he was engaging in the oppression of other species. Keshen introduced Singer to the Godlovitches, and in 1973 Singer reviewed their book for The New York Review of Books. In the review, he used the term "animal liberation", writing:

On the strength of his review, The New York Review of Books took the unusual step of commissioning a book from Singer on the subject, published in 1975 as Animal Liberation, now one of the animal rights movement's canonical texts. Singer based his arguments on the principle of utilitarianism – the view, in its simplest form, that an act is right if it leads to the "greatest happiness of the greatest number", a phrase first used in 1776 by Jeremy Bentham.^[80] He argued in favor of the equal consideration of interests, the position that there are no grounds to suppose that a violation of the basic interests of a human—for example, an interest in not suffering—is different in any morally significant way from a violation of the basic interests of a nonhuman.^[81] Singer used the term "speciesism" in the book, citing Ryder, and it stuck, becoming an entry in the Oxford English Dictionary in 1989.^[82]

The book's publication triggered a groundswell of scholarly interest in animal rights. Richard Ryder's Victims of Science: The Use of Animals in Research (1975) appeared, followed by Andrew Linzey's Animal Rights: A Christian Perspective (1976), and Stephen R. L. Clark's The Moral Status of Animals (1977). A Conference on Animal Rights was organized by Ryder and Linzey at Trinity College, Cambridge, in August 1977. This was followed by Mary Midgley's Beast And Man: The Roots of Human Nature (1978), then Animal Rights–A Symposium (1979), which included the papers delivered to the Cambridge conference.^[77]

From 1982 onwards, a series of articles by Tom Regan led to his The Case for Animal Rights (1984), in which he argues that nonhuman animals are "subjects-of-a-life", and therefore possessors of moral rights, a work regarded as a key text in animal rights theory.^[77] Regan wrote in 2001 that philosophers had written more about animal rights in the previous 20 years than in the 2,000 years before that.^[83] Garner writes that Charles Magel's bibliography, Keyguide to Information Sources in Animal Rights (1989), contains 10 pages of philosophical material on animals up to 1970, but 13 pages between 1970 and 1989 alone.^[84]

In 1971, a law student, Ronnie Lee, formed a branch of the Hunt Saboteurs Association in Luton, later calling it the Band of Mercy after a 19th-century RSPCA youth group. The Band attacked hunters' vehicles by slashing tires and breaking windows, calling it "active compassion". In November 1973, they engaged in their first act of arson when they set fire to a Hoechst Pharmaceuticals research laboratory, claiming responsibility as a "nonviolent guerilla organization dedicated to the liberation of animals from all forms of cruelty and persecution at the hands of mankind."^[85]

Lee and another activist were sentenced to three years in prison in 1974, paroled after 12 months. In 1976, Lee brought together the remaining Band of Mercy activists along with some fresh faces to start a leaderless resistance movement, calling it the Animal Liberation Front (ALF).^[85] ALF activists see themselves as a modern Underground Railroad, passing animals removed from farms and laboratories to sympathetic veterinarians, safe houses and sanctuaries.^[86] Some activists also engage in threats, intimidation, and arson, acts that have lost the movement sympathy in mainstream public opinion.^[87]

The decentralized model of activism is frustrating for law enforcement organizations, who find the networks difficult to infiltrate, because they tend to be organized around friends.^[88] In 2005, the US Department of Homeland Security indicated how seriously it takes the ALF when it included them in a list of domestic terrorist threats.^[89] The tactics of some of the more determined ALF activists are anathema to many animal rights advocates, such as Singer, who regard the movement as something that should occupy the moral high ground. ALF activists respond to the criticism with the argument that, as Ingrid Newkirk puts it, "Thinkers may prepare revolutions, but bandits must carry them out."^[90]

From the 1980s through to the early 2000s there was an increased level of violence by animal rights extremist groups directed at individuals and institutions associated with animal research. Activist groups involved included the Justice Department, the Animal Rights Militia and SHAC.^[91]

In the 1980s, animal rights became associated with punk subculture and ideologies, particularly straight edge hardcore punk in the United States^[92][93] and anarcho-punk in the United Kingdom.^[94] This association continues on into the 21st century, as evidenced by the prominence of vegan punk events such as Fluff Fest in Europe.^[95]

Henry Spira (1927–1998), a former seaman and civil rights activist, became the most notable of the new animal advocates in the United States. A proponent of gradual change, he formed Animal Rights International in 1974, and introduced the idea of "reintegrative shaming", whereby a relationship is formed between a group of animal rights advocates and a corporation they see as misusing animals, with a view to obtaining concessions or halting a practice. It is a strategy that has been widely adopted, most notably by People for the Ethical Treatment of Animals.^[96]

Spira's first campaign was in opposition to the American Museum of Natural History in 1976, where cats were being experimented on, research that he persuaded them to stop. His most notable achievement was in 1980, when he convinced the cosmetics company Revlon to stop using the Draize test, which involves toxicity tests on the skin or in the eyes of animals. He took out a full-page ad in several newspapers, featuring a rabbit with sticking plaster over the eyes, and the caption, "How many rabbits does Revlon blind for beauty's sake?" Revlon stopped using animals for cosmetics testing, donated money to help set up the Center for Alternatives to Animal Testing, and was followed by other leading cosmetics companies.^[97] Revlon has since renewed testing on animals as it is unwilling to give up revenue from sales in China, where animal testing is required for cosmetics and other items. [^[98]]

In 1999, New Zealand passed a new Animal Welfare Act that had the effect of banning experiments on "non-human hominids".^[99]

Also in 1999, Public Law 106-152 (Title 18, Section 48) was put into action in the United States. This law makes it a felony to create, sell, or possess videos showing animal cruelty with the intention of profiting financially from them.^[100]

In 2005, the Austrian parliament banned experiments on apes, unless they are performed in the interests of the individual ape.^[99] Also in Austria, the Supreme Court ruled in January 2008 that a chimpanzee (called Matthew Hiasl Pan by those advocating for his personhood) was not a person, after the Association Against Animal Factories sought personhood status for him because his custodians had gone bankrupt. The chimpanzee had been captured as a baby in Sierra Leone in 1982, then smuggled to Austria to be used in pharmaceutical experiments, but was discovered by customs officials when he arrived in the country, and was taken to a shelter instead. He was kept there for 25 years, until the group that ran the shelter went bankrupt in 2007. Donors offered to help him, but under Austrian law only a person can receive personal gifts, so any money sent to support him would be lost to the shelter's bankruptcy. The Association appealed the ruling to the European Court of Human Rights. The lawyer proposing the chimpanzee's personhood asked the court to appoint a legal guardian for him and to grant him four rights: the right to life, limited freedom of movement, personal safety, and the right to claim property.^[101]

In June 2008, a committee of Spain's national legislature became the first to vote for a resolution to extend limited rights to nonhuman primates. The parliamentary Environment Committee recommended giving chimpanzees, bonobos, gorillas, and orangutans the right not to be used in medical experiments or in circuses, and recommended making it illegal to kill apes, except in self-defense, based upon the rights recommended by the Great Ape Project.^[102] The committee's proposal has not yet been enacted into law.^[103]

From 2009 onwards, several countries outlawed the use of some or all animals in circuses, starting with Bolivia, and followed by several countries in Europe, Scandinavia, the Middle East, and Singapore.^[104]

In 2010, the regional government in Catalonia passed a motion to outlaw bull fighting, the first such ban in Spain.^[105] In 2011, PETA sued SeaWorld over the captivity of five orcas in San Diego and Orlando, arguing that the whales were being treated as slaves. It was the first time the Thirteenth Amendment to the United States Constitution, which outlaws slavery and involuntary servitude, was cited in court to protect nonhuman rights. A federal judge dismissed the case in February 2012.^[106]

In 2015, the Nonhuman Rights Project (NhPR) filed three lawsuits in New York State on behalf of four captive chimpanzees, demanding that the courts grant them the right to bodily liberty via the writ of Habeas Corpus and to immediately send them to a sanctuary affiliated with the North American Primate Sanctuary Alliance.^[107] All of the petitions were denied. In the case involving the chimpanzees Hercules and Leo, Justice Barbra Jaffe did not immediately dismiss the filing and instead ordered a hearing requiring the chimpanzee owner to show why the chimpanzees should be not be released and transferred to the sanctuary.^[108] Following the hearing, Justice Jaffe issued an order denying Hercules and Leo's petition.

Even though the petition was denied, NhRP interpreted Justice Jeffe's decision as a victory. In its press release it emphasized the fact that Justice Jeffe agreed with NhRP when finding that "'persons' are not restricted to human beings, and that who is a 'person' is not a question of biology, but of public policy and principle" and also stating that "Efforts to extend legal rights to chimpanzees are thus understandable; some day they may even succeed."^[109]

Robert Garner writes that both Hindu and Buddhist societies abandoned animal sacrifice and embraced vegetarianism from the 3rd century BCE. Several kings in India built hospitals for animals, and the emperor Ashoka (304–232 BCE) issued orders against hunting and animal slaughter, in line with ahimsa, the doctrine of non-violence. Garner writes that Jainism took this idea further. Jains believe that no living creature should be harmed, and they are known to clear paths in front of them by sweeping them to protect any insect life that may be present.^[110]

In 2014, the Jain pilgrimage destination of Palitana City in Indian state of Gujarat became the first city in the world to be legally vegetarian. It has outlawed, or made illegal, the buying and selling of meat, fish and eggs, and also related jobs or work, such as fishing and penning 'food animals'.^{[111][112][113][114]}

Paul Waldau writes that, in 2000, the High Court in Kerala used the language of "rights" in relation to circus animals, ruling that they are "beings entitled to dignified existence" under Article 21 of the Indian Constitution. The ruling said that if human beings are entitled to these rights, animals should be too. The court went beyond the requirements of the Constitution that all living beings should be shown compassion, and said: "It is not only our fundamental duty to show compassion to our animal friends, but also to recognize and protect their rights." Waldau writes that other courts in India and one court in Sri Lanka have used similar language.^[99]

In 2012, the Indian government issued a ban on the use of live animals in education and much research.^[115]

For some the basis of animal rights is in religion or animal worship (or in general nature worship), with some religions banning killing of any animal; One of the most important sanctions of the Jain, Hindu and Buddhist faiths is the concept of ahimsa, or refraining from the destruction of life. According to Buddhist belief, humans do not deserve preferential treatment over other living beings. See also in section above.

In contrast, in other religions, animals can be unclean, with in general allowing eating all except for these; "The Torah allows eating certain kinds of "winged swarming things" (i.e. insects) while prohibiting others".

The respect for animal rights in Jainism, Hinduism, and Buddhism derives from the doctrine of ahimsa.^[116][117] The Dharmic interpretation of this doctrine prohibits the killing of any living being.^[116]

Animal rights were recognized early by the Sharia (Islamic law). This recognition is based on both the Qur'an and the Hadith. In the Qur'an, there are many references to animals, detailing that they have souls, form communities, communicate with God and worship Him in their own way. Muhammad forbade his followers to harm any animal and asked them to respect the rights of animals.^[118] It is a distinctive characteristic of the Shariah that all animals have legal rights. Othman Llewellyn even argues that Shariah has mechanisms for the full repair of injuries suffered by non-human creatures including their representation in court, assessment of injuries and awarding of relief to them. The classical Muslim jurist 'Izz ad-Din ibn 'Abd as-Salam, who flourished during the thirteenth century, formulated the following statement of animal rights:

On the other hand, animal sacrifice is a prominent feature of Eid al-Adha observances.^[120]

The two main philosophical approaches to animal rights are utilitarian and rights-based. The former is exemplified by Peter Singer, and the latter by Tom Regan and Gary Francione. Their differences reflect a distinction philosophers draw between ethical theories that judge the rightness of an act by its consequences (consequentialism/teleological ethics, or utilitarianism), and those that focus on the principle behind the act, almost regardless of consequences (deontological ethics). Deontologists argue that there are acts we should never perform, even if failing to do so entails a worse outcome.^[121]

There are a number of positions that can be defended from a consequentalist or deontologist perspective, including the capabilities approach, represented by Martha Nussbaum, and the egalitarian approach, which has been examined by Ingmar Persson and Peter Vallentyne. The capabilities approach focuses on what individuals require to fulfill their capabilities: Nussbaum (2006) argues that animals need a right to life, some control over their environment, company, play, and physical health.^[122]

Stephen R. L. Clark, Mary Midgley, and Bernard Rollin also discuss animal rights in terms of animals being permitted to lead a life appropriate for their kind.^[123] Egalitarianism favors an equal distribution of happiness among all individuals, which makes the interests of the worse off more important than those of the better off.^[124] Another approach, virtue ethics, holds that in considering how to act we should consider the character of the actor, and what kind of moral agents we should be. Rosalind Hursthouse has suggested an approach to animal rights based on virtue ethics.^[125] Mark Rowlands has proposed a contractarian approach.^[126]

Nussbaum (2004) writes that utilitarianism, starting with Jeremy Bentham and John Stuart Mill, has contributed more to the recognition of the moral status of animals than any other ethical theory.^[128] The utilitarian philosopher most associated with animal rights is Peter Singer, professor of bioethics at Princeton University. Singer is not a rights theorist, but uses the language of rights to discuss how we ought to treat individuals. He is a preference utilitarian, meaning that he judges the rightness of an act by the extent to which it satisfies the preferences (interests) of those affected.^[129]

His position is that there is no reason not to give equal consideration to the interests of human and nonhumans, though his principle of equality does not require identical treatment. A mouse and a man both have an interest in not being kicked, and there are no moral or logical grounds for failing to accord those interests equal weight. Interests are predicated on the ability to suffer, nothing more, and once it is established that a being has interests, those interests must be given equal consideration.^[130] Singer quotes the English philosopher Henry Sidgwick (1838–1900): "The good of any one individual is of no more importance, from the point of view ... of the Universe, than the good of any other."^[81]

Singer argues that equality of consideration is a prescription, not an assertion of fact: if the equality of the sexes were based only on the idea that men and women were equally intelligent, we would have to abandon the practice of equal consideration if this were later found to be false. But the moral idea of equality does not depend on matters of fact such as intelligence, physical strength, or moral capacity. Equality therefore cannot be grounded on the outcome of scientific investigations into the intelligence of nonhumans. All that matters is whether they can suffer.^[131]

Commentators on all sides of the debate now accept that animals suffer and feel pain, although it was not always so. Bernard Rollin, professor of philosophy, animal sciences, and biomedical sciences at Colorado State University, writes that Descartes' influence continued to be felt until the 1980s. Veterinarians trained in the US before 1989 were taught to ignore pain, he writes, and at least one major veterinary hospital in the 1960s did not stock narcotic analgesics for animal pain control. In his interactions with scientists, he was often asked to "prove" that animals are conscious, and to provide "scientifically acceptable" evidence that they could feel pain.^[132]

Scientific publications have made it clear since the 1980s that the majority of researchers do believe animals suffer and feel pain, though it continues to be argued that their suffering may be reduced by an inability to experience the same dread of anticipation as humans, or to remember the suffering as vividly.^[133] The problem of animal suffering, and animal consciousness in general, arose primarily because it was argued that animals have no language. Singer writes that, if language were needed to communicate pain, it would often be impossible to know when humans are in pain, though we can observe pain behavior and make a calculated guess based on it. He argues that there is no reason to suppose that the pain behavior of nonhumans would have a different meaning from the pain behavior of humans.^[134]

Tom Regan, professor emeritus of philosophy at North Carolina State University, argues in The Case for Animal Rights (1983) that nonhuman animals are what he calls "subjects-of-a-life", and as such are bearers of rights.^[135] He writes that, because the moral rights of humans are based on their possession of certain cognitive abilities, and because these abilities are also possessed by at least some nonhuman animals, such animals must have the same moral rights as humans. Although only humans act as moral agents, both marginal-case humans, such as infants, and at least some nonhumans must have the status of "moral patients".^[135]

Moral patients are unable to formulate moral principles, and as such are unable to do right or wrong, even though what they do may be beneficial or harmful. Only moral agents are able to engage in moral action. Animals for Regan have "intrinsic value" as subjects-of-a-life, and cannot be regarded as a means to an end, a view that places him firmly in the abolitionist camp. His theory does not extend to all animals, but only to those that can be regarded as subjects-of-a-life.^[135] He argues that all normal mammals of at least one year of age would qualify:

Whereas Singer is primarily concerned with improving the treatment of animals and accepts that, in some hypothetical scenarios, individual animals might be used legitimately to further human or nonhuman ends, Regan believes we ought to treat nonhuman animals as we would humans. He applies the strict Kantian ideal (which Kant himself applied only to humans) that they ought never to be sacrificed as a means to an end, and must be treated as ends in themselves.^[136]

Gary Francione, professor of law and philosophy at Rutgers Law School in Newark, is a leading abolitionist writer, arguing that animals need only one right, the right not to be owned. Everything else would follow from that paradigm shift. He writes that, although most people would condemn the mistreatment of animals, and in many countries there are laws that seem to reflect those concerns, "in practice the legal system allows any use of animals, however abhorrent." The law only requires that any suffering not be "unnecessary". In deciding what counts as "unnecessary", an animal's interests are weighed against the interests of human beings, and the latter almost always prevail.^[137]

Francione's Animals, Property, and the Law (1995) was the first extensive jurisprudential treatment of animal rights. In it, Francione compares the situation of animals to the treatment of slaves in the United States, where legislation existed that appeared to protect them, while the courts ignored that the institution of slavery itself rendered the protection unenforceable.^[138] He offers as an example the United States Animal Welfare Act, which he describes as an example of symbolic legislation, intended to assuage public concern about the treatment of animals, but difficult to implement.^[139]

He argues that a focus on animal welfare, rather than animal rights, may worsen the position of animals by making the public feel comfortable about using them and entrenching the view of them as property. He calls animal rights groups who pursue animal welfare issues, such as People for the Ethical Treatment of Animals, the "new welfarists", arguing that they have more in common with 19th-century animal protectionists than with the animal rights movement; indeed, the terms "animal protection" and "protectionism" are increasingly favored. His position in 1996 was that there is no animal rights movement in the United States.^[140]

Mark Rowlands, professor of philosophy at the University of Florida, has proposed a contractarian approach, based on the original position and the veil of ignorance—a "state of nature" thought experiment that tests intuitions about justice and fairness—in John Rawls's A Theory of Justice (1971). In the original position, individuals choose principles of justice (what kind of society to form, and how primary social goods will be distributed), unaware of their individual characteristics—their race, sex, class, or intelligence, whether they are able-bodied or disabled, rich or poor—and therefore unaware of which role they will assume in the society they are about to form.^[126]

The idea is that, operating behind the veil of ignorance, they will choose a social contract in which there is basic fairness and justice for them no matter the position they occupy. Rawls did not include species membership as one of the attributes hidden from the decision makers in the original position. Rowlands proposes extending the veil of ignorance to include rationality, which he argues is an undeserved property similar to characteristics including race, sex and intelligence.^[126]

American philosopher Timothy Garry has proposed an approach that deems nonhuman animals worthy of prima facie rights. In a philosophical context, a prima facie (Latin for "on the face of it" or "at first glance") right is one that appears to be applicable at first glance, but upon closer examination may be outweighed by other considerations. In his book Ethics: A Pluralistic Approach to Moral Theory, Lawrence Hinman characterizes such rights as "the right is real but leaves open the question of whether it is applicable and overriding in a particular situation".^[141] The idea that nonhuman animals are worthy of prima facie rights is to say that, in a sense, animals do have rights. However, these rights can be overridden by many other considerations, especially those conflicting a human's right to life, liberty, property, and the pursuit of happiness. Garry supports his view arguing:

In sum, Garry suggests that humans have obligations to nonhuman animals; however, animals do not, and ought not to, have uninfringible rights against humans.

Women have played a central role in animal advocacy since the 19th century.^[143] The anti-vivisection movement in the 19th and early 20th century in England and the United States was largely run by women, including Frances Power Cobbe, Anna Kingsford, Lizzy Lind af Hageby and Caroline Earle White (1833–1916).^[144] Garner writes that 70 per cent of the membership of the Victoria Street Society (one of the anti-vivisection groups founded by Cobbe) were women, as were 70 per cent of the membership of the British RSPCA in 1900.^[145]

The modern animal advocacy movement has a similar representation of women, though Garner (2005) writes that they are not invariably in leadership positions: during the March for Animals in Washington, D.C., in 1990—the largest animal rights demonstration held until then in the United States—most of the participants were women, but most of the platform speakers were men.^[146] Nevertheless, several influential animal advocacy groups have been founded by women, including the British Union for the Abolition of Vivisection by Cobbe in London in 1898; the Animal Welfare Board of India by Rukmini Devi Arundale in 1962; and People for the Ethical Treatment of Animals, co-founded by Ingrid Newkirk in 1980. In the Netherlands, Marianne Thieme and Esther Ouwehand were elected to parliament in 2006 representing the Parliamentary group for Animals.

The preponderance of women in the movement has led to a body of academic literature exploring feminism and animal rights; feminism and vegetarianism or veganism, the oppression of women and animals, and the male association of women and animals with nature and emotion, rather than reason—an association that several feminist writers have embraced.^[143] Lori Gruen writes that women and animals serve the same symbolic function in a patriarchal society: both are "the used"; the dominated, submissive "Other".^[147] When the British feminist Mary Wollstonecraft (1759–1797) published A Vindication of the Rights of Woman (1792), Thomas Taylor (1758–1835), a Cambridge philosopher, responded with an anonymous parody, A Vindication of the Rights of Brutes (1792), claiming that Wollstonecraft's arguments for women's rights could be applied equally to animals, a position he intended as reductio ad absurdum.^[148]

Some transhumanists argue for animal rights, liberation, and "uplift" of animal consciousness into machines.^[149] Transhumanism also understands animal rights on a gradation or spectrum with other types of sentient rights, including human rights and the rights of conscious artificial intelligences (posthuman rights).^[150]

R. G. Frey, professor of philosophy at Bowling Green State University, is a preference utilitarian, as is Singer, but reaches a very different conclusion, arguing in Interests and Rights (1980) that animals have no interests for the utilitarian to take into account. Frey argues that interests are dependent on desire, and that no desire can exist without a corresponding belief. Animals have no beliefs, because a belief state requires the ability to hold a second-order belief—a belief about the belief—which he argues requires language: "If someone were to say, e.g. 'The cat believes that the door is locked,' then that person is holding, as I see it, that the cat holds the declarative sentence 'The door is locked' to be true; and I can see no reason whatever for crediting the cat or any other creature which lacks language, including human infants, with entertaining declarative sentences."^[151]

Carl Cohen, professor of philosophy at the University of Michigan, argues that rights holders must be able to distinguish between their own interests and what is right. "The holders of rights must have the capacity to comprehend rules of duty governing all, including themselves. In applying such rules, [they] ... must recognize possible conflicts between what is in their own interest and what is just. Only in a community of beings capable of self-restricting moral judgments can the concept of a right be correctly invoked." Cohen rejects Singer's argument that, since a brain-damaged human could not make moral judgments, moral judgments cannot be used as the distinguishing characteristic for determining who is awarded rights. Cohen writes that the test for moral judgment "is not a test to be administered to humans one by one", but should be applied to the capacity of members of the species in general.^[152]

Judge Richard Posner of the United States Court of Appeals for the Seventh Circuit debated the issue of animal rights in 2001 with Peter Singer.^[154] Posner posits that his moral intuition tells him "that human beings prefer their own. If a dog threatens a human infant, even if it requires causing more pain to the dog to stop it, than the dog would have caused to the infant, then we favour the child. It would be monstrous to spare the dog."^[153]

Singer challenges this by arguing that formerly unequal rights for gays, women, and certain races were justified using the same set of intuitions. Posner replies that equality in civil rights did not occur because of ethical arguments, but because facts mounted that there were no morally significant differences between humans based on race, sex, or sexual orientation that would support inequality. If and when similar facts emerge about humans and animals, the differences in rights will erode too. But facts will drive equality, not ethical arguments that run contrary to instinct, he argues. Posner calls his approach "soft utilitarianism", in contrast to Singer's "hard utilitarianism". He argues:

Roger Scruton, the British philosopher, argues that rights imply obligations. Every legal privilege, he writes, imposes a burden on the one who does not possess that privilege: that is, "your right may be my duty." Scruton therefore regards the emergence of the animal rights movement as "the strangest cultural shift within the liberal worldview", because the idea of rights and responsibilities is, he argues, distinctive to the human condition, and it makes no sense to spread them beyond our own species.^[7]

He accuses animal rights advocates of "pre-scientific" anthropomorphism, attributing traits to animals that are, he says, Beatrix Potter-like, where "only man is vile." It is within this fiction that the appeal of animal rights lies, he argues. The world of animals is non-judgmental, filled with dogs who return our affection almost no matter what we do to them, and cats who pretend to be affectionate when, in fact, they care only about themselves. It is, he argues, a fantasy, a world of escape.^[7]

Scruton singled out Peter Singer, a prominent Australian philosopher and animal-rights activist, for criticism. He wrote that Singer's works, including Animal Liberation, "contain little or no philosophical argument. They derive their radical moral conclusions from a vacuous utilitarianism that counts the pain and pleasure of all living things as equally significant and that ignores just about everything that has been said in our philosophical tradition about the real distinction between persons and animals."^[7]

Evolutionary studies have provided explanations of altruistic behaviours in humans and nonhuman animals, and suggest similarities between humans and some nonhumans.^[155] Scientists such as Jane Goodall and Richard Dawkins believe in the capacity of nonhuman great apes, humans' closest relatives, to possess rationality and self-awareness.^[156]

In 2010, research led by psychologist Diana Reiss and zoologist Lori Marino was presented to a conference in San Diego, suggesting that dolphins are second in intelligence only to human beings, and concluded that they should be regarded as nonhuman persons. Marino used MRI scans to compare the dolphin and primate brain; she said the scans indicated there was "psychological continuity" between dolphins and humans. Reiss's research suggested that dolphins are able to solve complex problems, use tools, and pass the mirror test, using a mirror to inspect parts of their bodies.^[157][158]

Studies have established links between interpersonal violence and animal cruelty.^[159][160]

In Christian theology, the founder of the Methodist movement, John Wesley, was a Christian vegetarian and maintained "that animals had immortal souls and that there were considerable similarities between human and non-human animals."^[161]

According to a paper published in 2000 by Harold Herzog and Lorna Dorr, previous academic surveys of attitudes towards animal rights have tended to suffer from small sample sizes and non-representative groups.^[162] However, a number of factors appear to correlate with the attitude of individuals regarding the treatment of animals and animal rights. These include gender, age, occupation, religion, and level of education. There has also been evidence to suggest that prior experience with companion animals may be a factor in people's attitudes.^[163]

Women are more likely to empathize with the cause of animal rights than men.^[163][164] A 1996 study of adolescents by Linda Pifer suggested that factors that may partially explain this discrepancy include attitudes towards feminism and science, scientific literacy, and the presence of a greater emphasis on "nurturance or compassion" among women.^[165]

A 2007 survey to examine whether or not people who believed in evolution were more likely to support animal rights than creationists and believers in intelligent design found that this was largely the case – according to the researchers, the respondents who were strong Christian fundamentalists and believers in creationism were less likely to advocate for animal rights than those who were less fundamentalist in their beliefs. The findings extended previous research, such as a 1992 study which found that 48% of animal rights activists were atheists or agnostic.^[166][167] A 2019 study in The Washington Post found that those who have positive attitudes toward animal rights also tend to have a positive view of universal healthcare, favor reducing discrimination against African Americans, the LGBT community and undocumented immigrants, and expanding welfare to aid the poor.^[168]

Two surveys found that attitudes towards animal rights tactics, such as direct action, are very diverse within the animal rights communities. Near half (50% and 39% in two surveys) of activists do not support direct action. One survey concluded "it would be a mistake to portray animal rights activists as homogeneous."^[163][169]