From Moral Issues that Divide Us


James Fieser


Revised: 9/1/2017






Animal Consciousness and Pain

Factory Farming

Animal Research

Animal Advocacy Groups

What People Think

Ethical Issues

Difference Between Animals and Humans: Three Positions

Indirect Duties to Animals: Locke and Kant

Animal Sentience: Singer

Animal Rights: Regan

Natural Order Argument for Eating Animals

Tacit Alliance Argument for Eating Animals

Replaceability Argument for Eating Animals

Public Policy Issues

Federal Animal Laws

State and International Animal Laws

Common Arguments Pro and Contra

The Conservative Position

The Liberal Position

A Middle Ground

Study Questions




A Dalmatian dog named Pepper disappeared one evening after the owners let it outside to roam around as they routinely did. For days the family searched for her throughout the area and, when nothing materialized, they began investigating the local network of illegal animal dealers. These people would troll the area gathering up stray animals, sometimes outright stealing pets from people’s back yards and sell them to laboratories for animal experiments.  With help from the SPCA and even the FBI, the family discovered that their dog was passed around from dealer to dealer and eventually sold to a hospital research facility for around $15. By then it was too late. Pepper had been cut open, implanted with an experimental pacemaker, and died when the procedure failed. Her body was then cremated. Pepper’s story and similar ones spread through the media, and outraged citizens pressured Congress to address the issue, which they eventually did in the passage of the country’s most important animal-protection law, the Animal Welfare Act of 1966.

             Anyone familiar with Pepper’s story would almost certainly side with the dog rather than the animal dealers. The familiarity that we have with our pets gives us a unique insight into the feelings and interests of animals. Yet at the same time we typically give little thought to the staggering number of animals that we use in for food, clothing, experimentation, and recreation, and what the animals themselves might be experiencing. While no non-human animal on this planet has the sophisticated rational abilities that we do, many have mental capacities that enable them to experience pain, suffering and anxiety from our treatment of them. In this chapter we will look at some of the more controversial ways that society treats animals, and whether animals might have rights that protect them from our conduct towards them.




The underlying problem with many of the uses of animals is that they cause them to experience pain. Our first line of inquiry, then, is to determine which if any animals are capable of experiencing pain. Next we must look at the specific pain-producing ways in which we treat those animals.


Animal Consciousness and Pain

How do we know which if any animals have the conscious capacity to feel pain? There are many different animals out there with varying degrees of neurological complexity, from primitive ones like worms, to sophisticated ones like chimpanzees. How do we get inside the minds of any of these to know what they are experiencing? This points to a larger problem of how we know the mental experiences of any conscious creature, whether it is a human, an animal, or an alien from outer space for that matter. The only mental experience that I can directly encounter is my own. If a rock falls on your foot, I cannot directly experience your thought process to know whether you are consciously feeling pain, and, so too if a rock falls on the foot of an animal. In fact, I cannot even say with complete certainty whether you or anyone else has a conscious mind at all since I cannot access anyone else’s mind directly. All I see is how you behave, but for all I know you are just an unconscious biological robot that is programmed to respond to certain stimulus, such as shouting “ouch” when a rock is dropped on your foot. This is what philosophers call the problem of other minds. Although the barrier between my mind and the minds of other people is a permanent one, there is nonetheless a partial solution to this problem. If there are enough physical and behavioral similarities between me and you, then I am justified in inferring that you have mental experiences just like I do. The solution, then, is one based on analogy, which can be expressed as follows:


1. When a rock falls on my foot, I consciously experience pain.

2. Joe has physical and behavioral features that are similar to mine.

3. Therefore, when a rock falls on Joe’s foot, he consciously experiences pain.


Since Joe and I are members of the same species and essentially identical physiologically, it is reasonable for me to conclude that Joe’s mental experiences are essentially the same as mine.

             To some extent, we can apply this same solution from analogy to the problem of animal consciousness and an animal’s experience of pain. Indeed, humans and animals are different species and physiologically distinct in many important ways, but there are still relevant physiological and behavioral still points of commonality. If the similarities between me and a cat are strong enough, it may be reasonable to conclude that the cat experiences pain the same way that I do. The more physical and behavioral features animals have in common with me, the more likely it is that they are conscious like me. When identifying similarities between how humans and animals experience pain, we often look at behaviors such as limping, whimpering, or making recognizable facial expressions of distress. These behaviors in animals, though, are not always reliable indicators of what is going on inside an animal’s mind since we can too easily read into these our own human experiences. A better test of whether an animal feels pain involves its physiology: the closer its biological pain mechanism is to that of humans, the more reasonable it is to assume that it experiences pain the way that we do. In humans, the experience of pain involves the presence of (1) pain receptors throughout our body, (2) neurological pain pathways within our brains, (3) natural painkillers that are released within the brain when pain increases, and (4) specific pain pathways to the association cortex, which gives the emotional aspect of pain.

             Which animals, then, have these pain mechanisms? Invertebrate animals, such as sea slugs, only have the first of these features, but lack the remaining ones which involve more sophisticated nervous systems. It appears, then, that their receptors operate as only stimulus-response reflex mechanisms, without involving any conscious experience of pain. The story is different with most vertebrate animals, though, particularly mammals, whose nervous systems are complex enough to support the first three of the above features, thereby implying that they consciously experience pain. As to emotional suffering, only a small number of mammals have an association cortex, and in smaller mammals such as mice it is almost nonexistent. But it is particularly prominent in chimpanzees and dolphins, which suggests that they might be capable of experiencing human-like suffering.

             Discussions of animal mental abilities often distinguish between higher and lower animals, which came to prominence in nineteenth-century writings in biology. Then, as now, the terms are informal ones with no agreed upon definition or consistent use. Writers of the time often designated human beings as higher animals, and all other creatures as lower ones. Others designated higher animals as non-human creatures with more sophisticated cognitive abilities such as chimps or dogs, and lower animals as cognitively less sophisticated ones such as lizards or chickens. Darwin alternated between these two uses in his writings. In recent times, the higher-lower distinction has been used in the updated biological tree of life to distinguish "lower" metazoan creatures like sponges and jellyfish from "higher" metazoans such as flatworms. The common use in ethical discussions today is the second of these, which follows this hierarchy: (1) humans, (2) higher animals such as chimps and dogs, (3) lower animals such as lizards and chickens.


Factory Farming

In the U.S., over 10 billion animals are raised and killed each year for food, about 9 billion chickens, 250 million turkeys, 100 million pigs, 35 million cows. The vast majority of these are not raised on small family farms but, rather, in large agricultural facilities called factory farms, also known as Confined Animal Feeding Operations (CAFOs). The idea of factory farming originated in the 1920s with the discovery of vitamins A and D. When mixed with feed, farm animals were capable of growing without sunlight or exercise, which enabled them to be raised more efficiently in barns throughout the year. With population growth and increases in meat eating, by the 1960s factory farming became widespread and today it dominates the meat production industry. The driving force behind factory farming is economics: it is cheaper to raise animals in a confined area using assembly-line methods than it is to manage them in larger and open areas. The meat industry is competitive, and to stay in business farmers need to adopt the most cost-effective methods of raising animals.

             In the process of cutting production costs, factory farming has been notoriously neglectful of animal welfare, and the main animals affected are cows, pigs, turkeys and chickens. The central problem is that an excessive number of animals are held in tightly confined areas, typically in metal buildings that allow no access to sunlight, fresh air, or vegetation, which prevents them from moving around or carrying out other normal behaviors. It is typical for feedlots to house thousands of cows, or egg-laying facilities to hold over a million chickens in small cages stacked several layers high. Many animals are so restricted that they cannot turn around to satisfy their natural inclinations of self-grooming. Within these tightly compressed areas, chickens often become aggressive and, to prevent them from pecking their neighbors, farmers clip off their beaks shortly after they are hatched. Diseases rapidly spread in these close and unsanitary living quarters, and, to combat this, antibiotics are mixed in with their feed. To maximize efficiency, animals are given growth hormones or specially bred to put on bulk, often to the point that their legs break under their weight. About 10% of factory farm animals die from disease, injury and stress, without ever making it to slaughterhouses. The enormous amounts of urine and feces from these animals is stored in large lagoons or sprayed on crops, which pollutes the air and contaminates groundwater.

             The principle products of factory farming are meat and dairy items. However, built into the economics of animal agriculture, all parts of slaughtered animals are used as ingredients in consumer products, as described here regarding the rendered byproducts of slaughtered cows:


the blood of a slaughtered cow is used to manufacture plywood adhesives, fertilizer, fire extinguisher foam, and dyes.  Her fat helps make plastic, tires, crayons, cosmetics, lubricants, soaps, detergents, cough syrup, contraceptive jellies and creams, ink, shaving cream, fabric softeners, synthetic rubber, jet engine lubricants, textiles, corrosion inhibitors, and metal-machining lubricants.  Her collagen is found in pie crusts, yogurts, matches, bank notes, paper, and cardboard glue; her intestines are used in strings for musical instruments and racquets; her bones in charcoal ash for refining sugar, in ceramics, and cleaning and polishing compounds. [Steven M. Wise, Drawing the Line: Science and the Case for Animal Rights, (2002)].


The life spans of all factory-farmed animals are short. While the normal life of a cow is 25 years, factory farm beef cattle are slaughtered at around age 1, and dairy cows at age 4. Pigs, which live to 15 years, are slaughtered at less than a year. Chickens, with a 7 year lifespan, are killed at 5 weeks for food and 2 years for egg-laying. As the egg-laying industry uses only hens, unwanted male chicks are killed as soon as they hatch, about 200 million a year, typically by being dropped alive into a grinding machine.


Animal Research

Over 25 million animals are killed each year in the US for animal testing, and the specific type of animal used depends upon the type of test that is performed. Around 90% of these are mice and rats, and about 1% (i.e., 250,000) are cats, dogs and primates. Other animals used in research are hamsters, guinea pigs, rabbits, chickens, sheep, horses and cows. There are three main purposes of animal testing. First is to advance scientific knowledge about animals themselves, such as their behavior and physiology. Second is to use animals as models for studying human diseases, such as viruses, and the effectiveness of human medicine. Third is to use animals as models for toxicity testing of drugs, food, cosmetics, and household chemicals; these experiments tell us whether a particular manufactured substance might be harmful or even lethal for humans. Almost all research animals are killed when the studies are complete.

             Inhumane treatment of laboratory animals can occur at every stage of their lives. There is distress from their early weaning, transporting them in unfamiliar and harsh conditions, housing them in cages for most of their lives, and restraining them during testing procedures, such as strapping a primate to a chair. Then there is the test procedure itself which involves administering a drug or chemical, or performing surgery. Toxicity tests are vivid examples. Suppose, for example, that a cosmetic company develops a new facial cream. To test for potential harm, researchers will apply the chemical agents in the cream to lab animals’ skin and eyes, feed it to them, and have them breathe its vapors. The chemical will be introduced in both low and high quantities to detect the point at which physiological problems might emerge. Specific problems might include skin rash, weight loss, nausea, pain, genetic damage, birth defects, organ failure, convulsions, coma, and death. Some animals will be subjected to long term exposure, about two years, to test for carcinogenicity. One controversial toxicity experiment is the Draize test, which involves placing a substance directly into the eyes of a live, conscious animal, usually an albino rabbit. While some countries are phasing out this particular procedure, it is still practiced in the U.S. Another is the lethal dose test, sometimes called LD50, which involves determining the amount of the substance in a single dose that will kill 50% of test animals, usually in a population of 60 subjects.

             To help limit the harm done to animals in laboratory experiments, some researchers advocate what are known as the Three Rs of humane animal experimentation: replacement, reduction, and refinement. The original creators of this standard explain what each means here:


Replacement means the substitution for conscious living higher animals of insentient material. Reduction means reduction in the numbers of animals used to obtain information of a given amount and precision. Refinement means any decrease in the incidence or severity of inhumane procedures applied to those animals which still have to be used. [William Russell Rex Burch, The Principles of Humane Experimental Technique (1959), Ch. 4]


With replacement, alternative laboratory tests might involve experimenting only on parts of animals, such as isolated cells, tissues, or organs. They might also test invertebrates such as horseshoe crabs in place of vertebrates and mammals, or they might study vertebrates only during early stages of fetal development. Computer models of living organisms are also becoming an option. With reduction, one effort would be to eliminate unnecessary duplication of animal experiments, which often occur when researchers are unaware of or do not have access to the data of earlier experiments. Researchers note that while needless redundancy should be eliminated, it is often important to replicate the same experiments as part of the scientific method whereby one researcher confirms the findings of another. With refinement, animal suffering can be reduced by giving them more natural environments and better anesthesia.


Animal Advocacy Groups

There are numerous animal advocacy organizations that seek to improve animal conditions in one way or another, and they are often categorizes as advocating either animal welfare and animal rights. Animal welfare, the weaker of the two, seeks to provide for the physical and mental needs of animals and avoid the infliction of unnecessary pain on them. This allows for human use of animals for food and experimentation, so long as the animals are treated humanely. Animal rights is the stronger position which maintains that animals, like humans, have non-negotiable rights to not be exploited for food, entertainment, experimentation, or similar uses.

             The most famous animal welfare groups are the Humane Society and the Society for the Prevention of Cruelty to Animals (SPCA). A prominent animal rights group is People for the Ethical Treatment of Animals (PETA), which devotes most of its resources to opposing factory farming, animal research, the animal clothing industry, and the animal entertainment industry. Their website contains especially graphic videos of animal mistreatment within these industries. Some organizations have particularly narrow focuses. For example, the Coalition for Consumer Information on Cosmetics (CCIC) opposes animal testing with cosmetics and lists companies that have adopted their "Corporate Standard of Compassion for Animals," thereby agreeing not to test on animals during any stage of product development.

             Another specialized group is the Great Ape Project, which seeks to secure legal rights for large primates, which are the closest genetic relatives to human beings, and share many of our mental and emotional characteristics. Founded in 1993, the Project hopes to take a census of all great apes worldwide, and, in the U.S., it seeks release of the 3,000 of them in captivity, almost half of which are used in biomedical research. The Project is lobbying the United Nations to enact a Declaration on Great Apes that includes the following:


We demand the extension of the community of equals to include all great apes: human beings, chimpanzees, bonobos, gorillas and orang-utans. The community of equals is the moral community within which we accept certain basic moral principles or rights as governing our relations with each other and enforceable at law. Among these principles or rights are the following: 1. The Right to Life. . . 2. The Protection of Individual Liberty. . .  3. The Prohibition of Torture. . . . []


New Zealand has enacted a version of the Great Ape Declaration.

             Some animal advocacy groups advance their causes through illegal tactics and are classified as domestic terrorists by the U.S. government, often with the designation of “animal enterprise terrorism.” The most famous of these is the Animal Liberation Front (ALF), and their activist guidelines include the following:


1. To liberate animals from places of abuse, i.e. laboratories, factory farms, fur farms, etc, and place them in good homes where they may live out their natural lives, free from suffering.

2. To inflict economic damage to those who profit from the misery and exploitation of animals.

3. To reveal the horror and atrocities committed against animals behind locked doors, by performing non-violent direct actions and liberations.

4. To take all necessary precautions against harming any animal, human and non-human. []


ALF members have vandalized fur stores, slaughterhouses, meat shops, animal breeding facilities, fast-food restaurants and circuses. They have conducted raids on animal testing facilities, releasing animals and stealing research videos of animal experiments. They have sent letter bombs and firebombed buildings. All of these activities, they maintain, are in the interests of freeing animals from mistreatment and making it financially unprofitable for companies and research institutions to harm animals.


What People Think

The surveys below suggest that people in the U.S. are generally concerned about animal protection, but are not ready to make big sacrifices on behalf of animals when it conflicts with human interests (from, 5/8-11/08).


"Which of these statements comes closest to your view about the treatment of animals? Animals deserve the exact same rights as people to be free from harm and exploitation. Animals deserve some protection from harm and exploitation, but it is still appropriate to use them for the benefit of humans. OR, Animals don't need much protection from harm and exploitation since they are just animals."

Same Rights As People: 25

Some Protection: 72

They are Just Animals: 3

Unsure: 1  


"Here are some specific proposals concerning the treatment of animals. For each one, please say whether you strongly support this proposal, somewhat support it, somewhat oppose it, or strongly oppose this proposal.”


"Passing strict laws concerning the treatment of farm animals"

Strongly Support: 35

Somewhat Support: 29

Somewhat Oppose : 20

Strongly Oppose: 13

Unsure: 3


"Banning all product testing on laboratory animals"

Strongly Support: 15

Somewhat Support: 24

Somewhat Oppose: 31

Strongly Oppose: 28

Unsure: 2


"Banning sports that involve competition between animals, such as horse racing or dog racing"

Strongly Support: 16

Somewhat Support: 22

Somewhat Oppose: 25

Strongly Oppose: 34

Unsure: 3


"Banning all medical research on laboratory animals"

Strongly Support: 13

Somewhat Support: 22

Somewhat Oppose: 31

Strongly Oppose: 33

Unsure: 1


"Banning all types of hunting"

Strongly Support: 8

Somewhat Support: 13

Somewhat Oppose: 29

Strongly Oppose: 48

Unsure: 1




We think of humans as members of a moral community where each one of us has moral worth. Whether animals also belong to that community depends upon how much they differ from us. If an animal is essentially the same as us, then it does belong, but if the animal is radically different, then maybe not. In this section we will look at those differences and the various theories of moral obligations to animals that follow from them.


Difference Between Animals and Humans: Three Positions

The first issue we will explore is the extent to which animals differ from humans with respect to their moral worth. The criteria of moral worth that philosophers consider are a mixed group, and often include the presence of a soul, the capacity for rationality, the ability to experience pleasure and pain, and displays of moral and social behavior. For simplicity, we will consider three ways of viewing differences in moral worth between humans and animals: the clear line position, the equality position, and the sliding scale position.

             First, the clear line position is that humans are unique among living creatures, and we alone have moral worth. The most famous philosophical defender of this view was French philosopher René Descartes (1596–1650), whose position hinges on a theory of mind called spirit-body dualism. According to Descartes, human beings are composed of two distinct types of substances: a physical body and a non-physical spirit-mind. Our physical bodies, he argues, are biological machines that follow strict laws of nature; our bodies are essentially robots without any capacity for conscious thought. Our spirit-minds, on the other hand, exist in a non-three-dimensional spirit realm and are responsible for our consciousness and reasoning. Descartes held that our spirit-minds are connected to our robotic bodies at a point in the center of our brains, which enables us to control our movements of our bodies the way that a puppeteer controls a puppet. But animals, he argues, are composed only of one substance, namely, a physical body, and completely lack a spirit-mind. The bodies of animals behave purely mechanically with no conscious mental activity whatsoever. Descartes recognized that some animals occasionally appear to have rational abilities, as when we train dogs to perform clever tricks, but these are still just robotic activities that dog trainers program into them. But, he argued, the clearest proof that animals have no spirit-mind is that they are incapable of expressing themselves in any language:


it has never yet been observed that any animal has arrived at such a degree of perfection as to make use of a true language. That is to say, they have not been able to indicate to us by the voice, or by other signs anything which could be referred to thought alone, rather than to a movement of mere nature. For the word is the sole sign and the only certain mark of the presence of thought hidden and wrapped up in the body. [Letter to Henry Moore]


On Descartes’ view, then, not only are animals not rational, but, lacking a spirit-mind as they do, they are not even conscious and thus are incapable of experiencing pain. If an animal acts as if it is in pain, it is only a reflexive action that is part of its biological programming.

             Second, the equality position is that human and many non-human animals have the same features of moral worth, and no meaningful distinctions can be drawn between them. It is unlikely that anyone seriously held that all animals, including single-celled ones such as amoebas, have equal moral worth with humans. Rather, it is a select group of animals, typically higher ones, that have this status. The oldest examples of the equality position are linked with reincarnation, the view that, upon the death of the body, the soul returns to earth in another body, either human or animal. Pythagoras is credited with being the first philosopher to introduce the concept of reincarnation into the ancient Greek world. A story relates that, when hearing a dog whimper when beaten by its owner, Pythagoras commanded the owner to stop since he recognized the voice of the dog being that of a deceased human friend (Diogenes Laertius, Lives, 8). Accordingly, he maintained that all animated beings are related and part of one great family.

             More recently, one of the strongest scientific claims for human-animal equality was made by Scottish physician William Lauder Lindsay (1829-1880). Humans, he argues, have persistently overrated our mental abilities relative to animals, and a careful examination of animal behavior and psychology shows that “The differences between the human and animal mind are sometimes scarcely or not at all perceptible, or they are in favour of the lower animals, not of man” (Mind in the Lower Animals, 1879, 1.1.10). Civilized humans indeed have superiority over animals with speech, use of hands, manufacturing and use of fire, but even here at least some of these advantages “are possessed by only a limited number of men—even of civilised men.” On the other hand, higher animals such as dogs that have been trained by humans “exhibit a manifest superiority to whole races or classes of man, both civilised and savage” with respect to the noblest human virtues. These include heroism, sympathy, charity, benevolence, forgiveness, self-control, repaying evil with good, industry, frugality, honesty, inventiveness, persistence, submission to law, moral sense, religious feeling, marriage, parenting, intelligence, sexual chastity, amiability, leadership, artistic sense, construction of dwellings, and many more. Lindsay concludes,


Man's claim to pre-eminence on the ground of the uniqueness of his mental constitution is as absurd and puerile, therefore, as it is fallacious. His overweening pride or vanity has led to his futile contention with the evidence of facts. He has trusted to a series of gratuitous assumptions. The supposed criteria of human supremacy, as the preceding chapter has shown, the alleged psychical distinctions between man and other animals, cannot stand examination.


It is thus only human arrogance that keeps us insisting that we are superior to animals.

             Finally, the sliding scale position is that there is a spectrum of moral worth among animals where humans are at the top, followed by higher animals, then lower animals. The most noteworthy advocate of the sliding scale position in biology is Charles Darwin who, in his Descent of Man, devotes two chapters to the distinctions between humans and animals. Like Lindsay, Darwin presents many examples of the sophisticated mental abilities that higher animals share with humans. They exhibit “jealousy, suspicion, emulation, gratitude, and magnanimity; they practise deceit and are revengeful; they are sometimes susceptible to ridicule, and even have a sense of humour; they feel wonder and curiosity” (Descent, 3). Darwin’s praise of their mental abilities is so strong that at times he appears to advocate the equality position. However, he stops short of that and argues instead that there is a series of gradations between animals and humans. The gap between the lowest fish and higher apes, he says, is much greater than that between those apes and humans. He concludes, then, that the distinction between animals and humans is one of degree, and not of kind:


There can be no doubt that the difference between the mind of the lowest man and that of the highest animal is immense. . . . Nevertheless the difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind. We have seen that the senses and intuitions, the various emotions and faculties, such as love, memory, attention, curiosity, imitation, reason, etc., of which man boasts, may be found in an incipient, or even sometimes in a well-developed condition, in the lower animals.” [Descent, 4]


             Unlike Lindsay, who believed that the moral qualities of trained animals equaled that of humans, Darwin argues that this too is a matter of degree. Animals that live in groups continually exhibit social instincts that are directed towards the general good or welfare of the community. They utter danger signals to warn others, defend their communities, give aid to their companions, have love and sympathy for them, are unhappy when separated from them and happy to return to them. However, while humans have all of these social instincts, we have a higher level moral capacity, the moral sense, which is built upon our moral instincts through our intelligence. The moral sense gives us the golden rule to do to others what we would want done to ourselves, and this “lies at the foundation of morality”. Darwin concludes that “The moral sense perhaps affords the best and highest distinction between man and the lower animals” (Descent, 4).

             How one treats animals is often a direct consequence of whether one holds the clear line, equality, or sliding scale view of an animal’s moral worth. An example of this with the clear line view is Descartes who would experiment on live animals, feeling confident that they were not conscious and capable of experiencing pain. In one case he writes to a colleague “If one had whipped a dog five or six times to the sound of the violin, as soon as it heard that music again it would begin to cry and run away” (Descartes to Mersenne, March 18, 1630). Other examples of Descartes’s live animal experiments are too grotesque to describe. By contrast, with the equality view, Pythagoras denounced all violence to animals with no exceptions:


Not only men of moderate abilities, but even first-rate sages and philosophers, such as Pythagoras and Empedocles, declare that all kinds of living creatures have a right to the same justice. They declare that unpardonable penalties loom over those who have done violence to any animal whatsoever. It is, therefore, a crime to injure an animal, and the perpetrator of such crime must bear his punishment. [Cicero, Republic, 3]


With the sliding scale view, Darwin took a middle ground. On the one hand, he writes, “I have all my life been a strong advocate for humanity to animals, and have done what I could in my writings to enforce this duty”. On the other, he continues, “I know that physiology cannot possibly progress except by means of experiments on living animals" (Darwin to Holmgren, April 14, 1881). To rectify these two sides, he actively sought legislation that would require anesthesia on animal subjects.

             The views of Descartes, Pythagoras and Darwin on the treatment of animals can easily be classified into the clear line, equality or sliding scale positions. Other philosophical theories about animal treatment are more nuanced, and we will turn to these next.


Indirect Duties to Animals: Aquinas, Locke and Kant

Let’s look again at the clear line position that humans are unique among living creatures, and we alone have moral worth. This is the most pessimistic view of animal mental abilities and any moral consideration that would go along with it. The question then arises whether this entitles us to treat animals any way that we want, as Descartes presumed that we could. Suppose that one evening you are walking your dog down the street and are attacked by a mugger. When attempting to get your wallet, he injures both you and the dog, but before he can do more he hears someone coming and runs off. Since you are a human being with moral worth, the mugger clearly did something wrong by injuring you. However, since your dog has no moral worth, did the mugger do anything wrong by injuring it? Thomas Aquinas, who held to the clear line view, argues yes the mugger did, but only because the dog is your property and the mugger in essence damaged your property. He writes,


He that kills another’s ox, sins, not through killing the ox, but through injuring another man in his property. For this reason this is not a case of the sin of murder but of the sin of theft or robbery. [Summa Theologica,]


The difference here is between what philosophers call direct and indirect duties. While the mugger has a direct duty to you because you have moral worth, the mugger has only an indirect duty to your dog since the dog lacks moral worth and its value is principally that of being your property. The two concepts are these:


Direct duty: an obligation I have to behave morally towards some person who has moral worth.

Indirect duty: an obligation I have to behave morally towards some being (e.g., a dog) because of how my behavior indirectly impacts some person who has moral worth (e.g., the dog owner).


The good news for the dog, then, is that it has some kind of moral protection, but the bad news is that the moral protection is only indirect and, in this case, the dog is protected only because it is your property. This would not help stray animals or animals whose owners are malicious. This problem came before the British Parliament two centuries ago, and one member put it this way. Suppose that you see someone abusing an animal and tell him to stop. If the abuser is not the animal owner, he could say “do you own the animal? If not, then mind your own business.” If, however, the abuser is indeed the animal owner, he still could say “I own it, so mind your own business.” Either way, there would be no grounds for intervening on behalf of the dog (Thomas Erskine, Cruelty to Animals, 1809).

             Thus, while property ownership is a good first start, it is not enough to generate a moral obligation to treat all animals humanely. Fortunately, there are other rationales for indirect duties towards animals, and we will look at four more. A second one is the distress caused to onlookers. For example, it is wrong for someone to abuse his dog in his front yard since it would distress passersby. Again, assuming that the dog itself has no moral worth as the clear line position maintains, the abuser has no direct obligation to the dog itself, but the abuser’s actions would indirectly distress viewers who have moral worth. This pushes animal protection a little further, but it does not block abuse of animals in private, such as with the mistreatment of animals within one’s home.

             A third rationale for indirect duties addresses private mistreatment of animals: it is wrong to privately torture an animal since this will create a bad habit that might later be directed towards humans. British philosopher John Locke (1632-1704) explains:


the custom of tormenting and killing of beasts will, by degrees, harden their minds even towards men; and they who delight in the suffering and destruction of inferior creatures, will not be apt to be very compassionate or benign to those of their own kind. Our practice takes notice of this, in the exclusion of butchers from juries of life and death. [Thoughts Concerning Education, 1693, 116]


The psychological connection between cruelty to animals and cruelty to humans was famously depicted in a series of engravings by British artist William Hogarth (1697–1764) titled “The Four Stages of Cruelty”. In the first stage, a boy named Tom Nero tortures birds, cats and dogs in plain view of everyone. As a young man, he then progresses in the second stage to beating a horse, then in the third stage to assaulting and killing his pregnant lover. In the fourth stage, after being found guilty of murder, Nero is hanged, and his body is dissected by surgeons. Hogarth himself writes “The prints were engraved with the hope of, in some degree, correcting that barbarous treatment of animals, the very sight of which renders the streets of our metropolis so distressing to every feeling mind” (Ireland, Hogarth Illustrated, 1812, 3). Psychological studies today support Locke’s and Hogarth’s intuition that a history of animal cruelty in childhood is associated with psychiatric disorders and criminal behavior in adulthood (Gleyzer, “Animal Cruelty,” JAAPL, 2002).

             So far, the rationales for indirect duties towards animals have focused on preventing mistreatment of them, both publicly and privately. But we can push this further and show how humans benefit when we actively treat animals benevolently, and not merely avoid mistreating them. A fourth rationale, then, is that it is right to publicly show kindness towards animals since this will make spectators happy. If I see that my neighbor’s dog is well-cared for and happy, it makes me happy. If I show kindness towards my neighbor’s dog such as by petting it, it makes my neighbor happy. First responders know the importance of showing kindness towards animals while on the job. If firefighters rescue a person from a burning house, they need to grab the cat on the way out, otherwise the owner will just run back in to get it.

             By pushing Locke’s view further, we can develop yet a fifth rationale: it is right to privately show kindness towards animals since this will create a good habit that might later be directed at humans. If I show compassion to a dog, I will be more inclined to do so with humans. Many prisons have put this concept into practice by using animal-assisted therapy as a means of increasing sociability and responsibility among inmates, and reducing repeat criminal offenses. On face value, these five rationales for indirect duties towards animals cover a lot of moral ground and give a respectable amount of protection to animals even when they lack moral worth.

             Consider now two criticisms of the idea of indirect duties to animals. First, American philosopher Robert Nozick (1938-2002) questions the psychological connection between mistreatment of animals and mistreatment of humans. If someone follows the clear line position and keeps in mind the distinction between humans and animals, Nozick asks, “why should killing animals tend to brutalize him and make him more likely to harm or kill persons?” Butchers do not seem to commit more murders than other people who have knives around. Also, if I enjoy hitting a baseball with a bat, that in and of itself does not mean that “I significantly increase the danger of my doing the same to someone’s head” (Anarchy, State and Utopia, 1974, 3). What we need, he argues, is a plausible explanation of how cruelty to animals leads to cruelty to humans, if in fact it does.

             In response, one such plausible explanation was offered by German philosopher Immanuel Kant (1724-1804), who agrees with Locke’s and Hogarth’s contention that mistreating animals leads to mistreating humans. In Kant’s words, “animals bear an analogy to human nature. We then observe duties to humanity when we observe duties towards those analogies, and we indirectly carry out our duties towards humanity” (Lectures on Ethics, 1785). For Kant, there is a strong similarity between human-human interaction and human-animal interaction. Suppose that your servant has grown old and can no longer perform his normal responsibilities. He deserves to be rewarded for his faithful service to you, and you must continue looking after him until he dies. Suppose now that your dog has grown old and can no longer perform its functions such as guarding the house or hunting. This parallels the case of the servant, and you cannot just shoot the dog because it is no longer useful to you. Kant writes, “even though this violates no direct duty to the dog, it damages the general moral idea of merit where we properly compensate people for their service”. Contrary to Nozick, there is no similar parallel between hitting a baseball and hitting a person’s head. There is also no parallel between a butcher who uses a knife to cut meat from an already dead cow, and a person who uses a knife to murder someone. So much for Nozick’s objection.

             The second criticism is that indirect duties by themselves are too weak to form the bases of consistent moral obligations to animals. If we take together all five of the above rationales for indirect duties, this might support welfare policies towards animals, such as bans on animal cruelty. When pressed, it might even support vegetarianism and bans on animal experimentation. However, the support they give does not rise to the level of urgency that morality often demands. Consider the following two rationales for not torturing animals:


• Direct duties to animals: torturing a dog is wrong since the dog is a conscious creature with moral worth, just like human beings are.

• Indirect duties to animals: torturing a dog is wrong since the idea of it distresses people, and such behavior might incline the abuser to harm humans.


The first rationale from direct duties is clearly stronger in that it makes a claim that is exceptionless: it is always wrong to torture a dog. By contrast, the second rationale from indirect duties is only a rule of thumb about how people typically behave to which there may be exceptions. This invites the torturer to view his own behavior differently if he only tortures animals in private, and he is careful about drawing a line between treatment of animals and treatment of humans. Urgent moral judgments require urgent justifications, and the above five rationales for indirect duties to animals lack that. Having said that, though, this does not mean that indirect duties are useless, since they can be an important supplement to direct duties. You should be nice to my child because of how it directly affects my child but also for how it indirectly affects me. So too with how you treat my dog. Further, if it happens that you do not believe that we owe dogs any direct duties, the indirect rationale is still there as a backup.


Animal Sentience: Singer

The term “sentience” means the capacity to experience pleasure and pain, and we turn next to the theory that animals have moral worth because they are sentient. From what we know about animal physiology today, it seems obvious that higher and many lower animals are sentient. However, it is a big step beyond that to hold that animals have moral worth because of that sentience. The first writer in modern times to hint at this was British utilitarian philosopher Jeremy Bentham (1748-1832). Bentham acknowledges that we may have good reason to eat animals if their deaths are quick and painless. We may also have good reason to kill animals in self-defense. However, he maintains, there is no reason to torment them and many reasons not to do so. Just as the rights of enslaved humans are becoming recognized, he argues, “The day may come, when the rest of the animal creation may acquire those rights which never could have been withholden from them but by the hand of tyranny.” When seeking out the factor that determines whether a being has such rights, “The question is not, Can they reason? nor, Can they talk? but, Can they suffer?” (Principles of Morals and Legislation, 1789, 17.1). The critical point, for Bentham, is that a being has moral worth if it is sentient, and animals are sentient. As a utilitarian, Bentham held that morally right actions are those that bring about the most pleasure for the most people. When determining whether an action is right or wrong, we should tally the amount of pleasure and pain our actions cause. Since animals experience pleasure and pain, then we must factor their interests into the equation.

             Bentham never fully developed his view that animal interests should factor into utilitarian moral decisions, and in fact his only discussion of the subject appears in a footnote. The task of expanding on Bentham’s view was taken up by contemporary Australian philosopher Peter Singer (b. 1946). There are two parts to Singer’s utilitarian view of animal ethics. First, all sentient creatures have an interest in avoiding pain, and we must give equal consideration of that interest for any sentient being that has the same degree of suffering as another sentient being. Suppose, for example, that I am in a room with a mouse and a mad scientists says that either I or the mouse must undergo 5 units of suffering. Since I and the mouse have equal consideration of interests, I cannot say “do it to the mouse since I am more important than it is.” If I use this line of reasoning, then I am a “speciesist”, which Singer describes here:


speciesists give greater weight to the interests of members of their own species when there is a clash between their interests and the interests of those of other species. Human speciesists do not accept that pain is as bad when it is felt by pigs or mice as when it is felt by humans. [Practical Ethics, 2011, 3]


Sentience, he says, is the sole basis for extending the principle of equality to nonhuman animals, and to give preference to members of our species would be as arbitrary as giving preference to one’s race.

             The second part of Singer’s view is that we must treat sentient beings differently based on their differing interests. Specifically, some sentient beings have a personal interest in continuing to live, and others do not. Sentient beings like humans and higher animals have that interest because they are “rational and self-conscious, conceiving themselves as distinct beings with a past and a future”. Killing these beings, then, is wrong. However, with sentient beings that are not rational or self-conscious, such as chickens or even a disabled human infant, “the case against killing is weaker”. In these situations, the wrongness of killing would be based on the loss of pleasure they would experience. If their lives are on the whole unpleasant, then painlessly killing them may be justifiable. But even when a chicken might live a pleasant life, it is possible that “no wrong is done if the animal killed will, as a result of the killing, be replaced by another animal living an equally pleasant life” (ibid, 5).

             Thus, if we were to classify Singer’s theory according to the three positions discussed earlier, he follows the equality position insofar as we must give equal consideration to all sentient beings, including non-human ones. However, he also follows the sliding scale position insofar as non-rational sentient beings are treated differently depending on their particular interests.

Is speciesism as arbitrary and unjustifiable as Singer maintains? American philosopher Roger Wertheimer (b.1942) thinks not, and argues that we have good reasons for preferring the human species above animal species. When each of us attempts to identify who we are as existing things, we first do so by considering what species category we belong to, and our moral identities will follow from that:


Our species category is our key concept for understanding ourselves metaphysically, scientifically, biologically, psychologically, socially. So it is naturally inevitably our principal and principled category of self-identification and public identification, politically, legally and morally. [“Slandering Speciesism” 2005]


The Golden Rule is an example of this since I must have some conception of who I am and who you are before I “do to others as a would like them to do to me.” It is our species that informs us of our identities to apply this moral principle, and there is nothing arbitrary about that. Thus, speciesism is justified since our morality needs a strong connection with our species. Let’s refer to this as Wertheimer’s “Plan A” conception of morality. But, Wertheimer continues, even this “Plan A” notion of morality is speciesist, in special circumstances “we also have need of a species-neutral notion of persons” so that, at least in theory, we could interact with alien creatures in an environment like the Star Wars cantina. That species-neutral conception of morality would be grounded in claims that we and the aliens make to each other and contractual agreements that we arrive at. For example, I will insist to the alien that he cannot eat me for dinner, he will make a similar claim about himself, and we will contractually agree to not eat each other. Let’s call this Wertheimer’s “Plan B” conception of morality. This “Plan B” contractual arrangement may work well between humans and rational aliens, but not so between humans and animals. He writes, “I doubt that we’re obliged to assign civil rights to any primates, however voluminous their lexicon, till some learn how to say and mean ‘I promise’ in some language.” Thus, according to Wertheimer, our “Plan A” for morality is speciesist, and our “Plan B” is based only on rational contracts in a species-neutral context. In either case, there is no moral equality for animals.

             So, between Wertheimer and Singer, who wins the contest between speciesism and anti-speciesism? Perhaps neither, since both species and sentience may only be parts of the larger and more fluid picture of morality. That is, species may be important when dealing with humans, sentience with other creatures, and contracts with still others. Imagine that you and I walked into the Star Wars cantina and discovered that the strange creatures present are of two sorts, each of which lacks an important feature of humanity. On one side of the room there are Cognizers who are conscious rational beings with no capacity to experience pleasure or pain, either physical or emotional. You try socializing with them, but they inflict pain on you by knocking into you, walking on your feet, and pointing out every flaw you have. They are not being malicious, it’s just who they are. However, they alter their behavior when you rationally negotiate with them your claim to be free from unnecessary pain. On the other side are Sentimentizers who are sentient yet rationally limited, comparable to a dog, and you then try socializing with them. They intuitively recognize your need to be free from pain, are gentle and even affectionate to you. You in turn show kindness to them, in essence, applying the Golden Rule.

             In this scenario, your morality is split between the rational Cognizers and the sentient Sentimentizers, depending on which side of the room you are on. When with the Cognizers you follow Wertheimer’s “Plan B” morality by rationally negotiating contracts, and when with the Sentimentizers you follow Singer by acknowledging their sentience. When with just me, you follow Wertheimer’s “Plan A” morality by having both sides of your in play. In the Star Wars scenario, it is unrealistic to cling to your unified morality and pretend that your interaction with both sets of aliens is not genuinely moral. Similarly, while on earth, when we interact with non-rational sentient animals, we set aside our unified morality and engage in the pleasure-pain morality of a sentient creature. Perhaps in the future when we interact with non-sentient rational robots, we will again set aside our unified morality and engage in the purely contract-based morality of a rational creature. There is no telling what kinds of unusual beings will emerge from genetic engineering or artificial intelligence research that will challenge our human species morality. But if and when that day comes, the best morality will be the one that can find common ground, rather than insist on exclusive litmus tests of species, sentience or rationality.


Animal Rights: Regan

We turn next to the view that animals have full-fledged moral rights, just as human beings do, and we should thus not harm or exploit them any more than we would a human. We find an early indication of this view in the ancient philosopher Porphyry (233-305) who argues in a straight forward way that animals are rational and, for that reason, deserve justice in the same way that humans deserve it. For Porphyry, animals can communicate with themselves, understand instructions from humans, strategically defend themselves, and live in communities, all of which are signs of reason. “Since justice pertains to rational beings, how can we avoid admitting that we should also act justly towards animals?” (On Abstinence from Killing Animals, 3). But Porphyry is speaking here of the “justice” that we owe animals, and it was not until the eighteenth-century that the moral and political concept of “rights” emerged. When it did, it was applied only to humans, as we see in the U.S. Declaration of Independence, and it took a century before animal advocates spoke of animal rights.

             While discussions of animal rights were common during the nineteenth and early twentieth centuries, they were not philosophically developed, and the task of changing that was taken on by American philosopher Tom Regan (1938-2017). In the Preface to his book The Case for Animal Rights (1983), Regan states, “My hope was to write, in clear, intelligible terms, a book that would lay the philosophical foundations of the animal rights movement as I conceive it”. His view of animal rights rests on two claims: (1) at least some animals have moral worth because of their mental abilities, and (2) this moral worth gives them moral rights. As to the first of these claims, he argues that the criterion of moral worth is that a being is an “experiencing subject of life”, that is, each of us has a life that matters to us. He describes this here:


individuals are subjects-of-a-life if they have beliefs and desires; perception, memory, and a sense of the future, including their own future; an emotional life together with feelings of pleasure and pain; preference- and welfare-interests; the ability to initiate action in pursuit of their desires and goals; a psychophysical identity over time; and an individual welfare in the sense that their experiential life fares well or ill for them, logically independently of their utility for others and logically independently of their being the object of anyone else's interests [The Case for Animal Rights, 7]


Thus, to be an “experiencing subject of a life”, a conscious creature must have the mental capacity to prefer, believe, feel, recall, and expect things. What is important, for Regan, is that there is a subject, or an “I” behind the preferences, beliefs and feelings that we have. It is this larger ability to view the world through our first-person perspective that gives us moral worth. Humans have this capacity, and, he argues, so too do many animals.

             As to the second claim, that “experiencing subjects of a life” have rights, it comes down to the issue of respect. As “experiencing subjects of a life”, you and I have a right to have our most basic interests respected, and not be used for other people’s benefits. He writes,


If The Case [for Animal Rights] has a central thesis, it is the respect principle, according to which all subjects-of-a-life, both human and nonhuman, share the fundamental right to be treated with respect. From this it follows that no subject-of-a-life may be harmed merely on the grounds that others will benefit.


Humans, along with some animals, are “somebodies”, and not things. This basic right to be treated with respect is the foundation of other important rights, such as the right not to be harmed.

             Regan rejects rival theories of animal ethics for overlooking an animal’s status as an “experiencing subject of a life” and, thus, not going far enough in protecting animal rights. For example, theories of indirect duties demote animals to a lower moral status by viewing them as "merely a sort of moral warm-up” to how we treat humans. But this, Regan argues, is arbitrary since it ignores the intuitively obvious fact that they have a capacity for mental experiences, which places a direct duty on us to not harm them. Singer’s utilitarian theory of sentience is admittedly a step better since it gives animals a direct moral status because of an animal’s mental capacity to have feelings. However, according to Regan, Singer only places value on the immediate feelings that an animal has, and not the animal itself in a larger sense. Regan gives an analogy of a cup that holds a sweet tasting liquid, where the cup is an animal and the liquid is the animal’s feelings. For Singer, it is only the liquid that has value, and not the cup. But, according to Regan’s notion of moral worth, “it’s the cup, not just what goes into it, that is valuable”.

             Consider now a criticism of Regan’s view of animal rights by American philosopher Carl Cohen. If animals had rights, Cohen argues, then we humans would have to prevent lions from eating zebras, just as we would stop lions from eating a human baby, which would be absurd to do. Animals live in an amoral realm where one animal does not have any rights claims against others. In Cohen’s words, "Rights are of the highest moral consequence, yes; but zebras and lions and rats are totally amoral; there is no morality for them; they do no wrong, ever. In their world there are no rights" ("Do Animals Have Rights", 1997). Regan’s response to this problem is that, while we certainly have moral obligations to protect our children from animal predators, we should otherwise just leave wild animals alone so that they can carve out their own destinies:


Our ruling obligation with regard to wild animals is to let them be, an obligation grounded in a recognition of their general competence to get on with the business of living, a competence that we find among members of predator and prey species. . . . As a general rule, they do not need help from is in the struggle for survival, and we do not fail to discharge our duty when we choose not to lend our assistance. [The Case for Animal Rights, 2004, Preface]


It is thus not the concern of wildlife managers to monitor the overall happiness of creatures in the wild, but, rather, to make sure that human activity does not make things worse for them.

             But Regan’s response does not fully address Cohen’s problem. If the rights of individual animals are the same as individual humans, then the individual zebra should be rescued from the lion just as we would a human child. After all, you would certainly rescue the zebra from the lion if the zebra was your personal property, and, as Regan himself suggests, extending rights to your zebra should give it better protection than merely acknowledging your indirect duty towards it as your property. There is a genuine conflict here between the full-fledged rights of animals and the practical necessity of animals eating each other in the wild. The blind forces of evolution have produced a brutal environment where so much of animal life depends upon eating other animals alive. However, this harsh reality could have been different if all animal species had evolved has herbivores, with no carnivores whatsoever. Imagine now a science fiction scenario where biologists would redesign the DNA of all animal life on this planet to be just that way. Fish would eat seaweed, cats would eat grass, crocodiles would eat plants. Further, these biologists would understand the tiniest facts about the delicate balance between life forms within ecosystems, so that the environment itself did not collapse when making these alterations. This would indeed resolve the conflict between animal rights and carnivorous behavior of wild animals. The moral question raised by this scenario is this: if we had the same knowledge and capability as these futuristic biologists, would we be morally required to change all animal carnivores into herbivores? On Regan’s view, the answer should be yes. In the world we currently inhabit, we are far from having the ability or the motivation to carry out this plan, and probably never will. However, like other possibly unachievable moral goods such as world peace or social justice, that should not prevent us from acknowledging what full rights for all animals would ideally involve.


Natural Order Argument for Eating Animals

An issue that is central to the animal ethics debate is whether it is permissible to eat animals, and there are a variety of terms that deal with such dietary restrictions. The most popular one is vegetarianism, which is a dietary practice that excludes all meat, including red meat, poultry and seafood, but includes eggs and milk products. A study published in Vegetarian Times states that 3.2% of the U.S. adult population are vegetarian. Veganism is a vegetarian diet that excludes egg and milk products. Pescetarianism is an otherwise vegetarian diet that also includes fish or other seafood, but not meat from other animals. Related to this is an activist movement called animal abolitionism which seeks to abolish all uses of animals in human food consumption. Some arguments against meat eating follow from the animal ethics theories that we have already examined. If obligations to animals are indirect, then it is wrong to treat animals as mere things to use and eat since this will make us more abusive to humans. If sentience is the foundation of morality as Singer suggests, then it is wrong to submit animals to a process of food production that is inherently painful for animals. If animals have non-negotiable rights as Regan suggests, then it is just as wrong to raise and kill an animal for food as it would be a human. In this section and the following ones, we will look at three arguments in support of meat eating that are debated by philosophers: the natural order argument, the tacit alliance argument, and the replaceability argument.

             The most common of these is the natural order argument. Even a superficial examination of the natural world shows that living things survive by eating other living things, where larger animals consume smaller ones. Aquinas argues that there is an established hierarchy of life forms in nature so that the lower imperfect forms may be killed and eaten by the higher more perfect forms. Accordingly, plants are to be killed by animals for food, and animals in turn are to be killed by humans for food. Further, he argues, plants and animals lack reason and exhibit motion “by a kind of natural impulse.” This shows that they are “naturally enslaved” and for that reason are “accommodated to the uses of others” (Summa Theologica,

             In criticism of the natural order argument, Greek historian Plutarch (46-120 CE) rejects the idea that meat eating comes naturally to humans. If you think it does, Plutarch says, then try killing and eating an animal with only your claws and teeth the way that wolves and lions do. It quickly becomes clear that our bodies were not naturally designed for this. Worse yet, try eating an animal while it is still alive like wild carnivores do. We are not mentally equipped to do that either. When we consider the birds that we kill for food, their beauty and charm suggests that they exist to be admired, not to be eaten. We also find the taste of meat disgusting, which is why we “smother the slaughtered gore with thousands of sauces, thereby tricking the palate so that it may accept such repulsive food.” People often ask what made the first vegetarian give up eating meat, but, Plutarch argues, the better question is what prompted the first meat eater to consume an animal as food:


How could his eyes withstand the blood of slaughtered, flayed, and mangled bodies? How could his nose bear their stench? How could its very foulness not upset his sense of taste while he chews the sores of animals, and swallows the juices and liquids of their deadly wounds? [“On Meat Eating”]


Plutarch believes that early people were driven to meat eating, not through any natural pleasure they would get from it, but through sheer necessity as they struggled to survive. Plutarch’s point is reiterated in our own times by PETA which holds that, biologically and anthropologically speaking, humans are herbivores that are ill-suited for meat eating. For, they argue, “humans lack both the physical characteristics of carnivores and the instinct that drives them to kill animals and devour their raw carcasses” ( Further, modern studies suggest that several features of our physiology are especially well-adapted for plant diets. For example, humans have significantly longer digestive tracts than do carnivores like lions, which makes ours more suited for digesting plants that require more time to process (Rob Dunn, "Human Ancestors Were Nearly All Vegetarians," 2012).

             However, while much of what Plutarch says about humans and meat eating may be true, the fact remains that we and our hominid ancestors have been eating meat for a long time, 3.3 million years by some accounts, and this impacted the evolution of the human body. Originally, primates were herbivores and had large jaws and teeth for grinding plants throughout the day. But, according to one study, when early hominids added cut and ground meat to their diets, they did not have to chew as much as large-jawed herbivore primates, and consequently our ancestors could evolve smaller jaws and teeth (Lieberman, “Impact of Meat”, Nature, 2016). Thus, while meat eating may not be natural to our most ancient primate history, it is to our more recent hominid development. Consequently, while we retain some of the non-meat-eating physical features that Plutarch notes, we also have newer meat-eating features. The issue of whether meat eating is natural to us is now not so simple, and plain appeals to our natural design may not establish the issue one way or another. We naturally have the option of going in either direction, and if there is a moral question about which is preferable, it must be settled some other way.


Tacit Alliance Argument for Eating Animals

The second argument for meat eating is that of tacit alliance: it is better for an animal to be raised and killed for human use than to not exist at all. As British philosopher Leslie Stephen (1832-1904) states it,


Of all arguments for vegetarianism, none is so weak as the argument from humanity. The pig has a stronger interest than any one in the demand for bacon. If all the world were Jewish, there would be no pigs at all. He has to pay for his privileges by an early death; but he makes a good bargain of it. [“Ethics and the Struggle for Existence” 1896]


There is, in a sense, a tacit alliance, or unspoken arrangement between humans and pigs, where we benefit from eating them for food while they benefit by being alive even for a limited amount of time and being maintained by us. This, Stephen argues, is precisely how species in the wild maintain a reciprocal dependence: “If the wolf ate all the sheep, and the sheep ate all the grass, the result would be the extirpation of all the sheep and all the wolves, as well as all the grass.” For both wolves and sheep to survive, there needs to be an environmental equilibrium maintained between the two, which nature maintains when sheep starve since there is not enough grass, and wolves starve when there are not enough sheep. Humans, as rational creatures with foresight, recognize these tacit alliances among species and we can plan for them. We do like sheep, though, so we maintain the numbers that we need. Since wolves also eat sheep, we see them as enemies and reduce their numbers. Thus, “If the wolf is extirpated as an internecine enemy, it is that there may be more sheep when sheep have become our allies and the objects of our earthly providence.” According to Stephen, pigs have lucked out since we like bacon, and we prefer to cultivate pigs in large numbers, as opposed to limiting them in favor of some other animal that we might better prefer.

             There are two criticisms of Stephen’s tacit alliance argument. First, as Henry Salt argues, it places non-existing pigs within the same moral category as existing pigs. According to Salt, the tacit alliance argument is the same rationale is used by sportsmen who “preserve” the fox for foxhunting, and the experimenter who breed guinea-pigs for experimentation. This logic is also used as an excuse for breeding slaves: it is better that they live as slaves rather than not living at all. If you asked the slave, he might even agree. However, according to Salt, it is nonsense to negotiate such an agreement with a thing that does not yet exist. The whole issue rests on a fallacy that attempts to compare the current existence of a pig or a slave to their prior non-existence:


A person who is already in existence may feel that he would rather have lived than not, but he must first have the terra firma of existence to argue from; the moment he begins to argue as if from the abyss of the non-existent, he talks nonsense, by predicating good or evil, happiness or unhappiness, of that of which we can predicate nothing. [“The Logic of the Larder,” The Humanities of Diet, 1914]


Suppose that we say that even a pig has 5 units of happiness during its short life on a farm, and that, by contrast, a non-existent pig has zero units. The comparison is flawed since a non-existent pig is not really a thing at all and we cannot ascribe even zero units of happiness to a non-thing.

             Salt is right that you cannot assign even a zero value of happiness to a non-existent pig. But the point that Stephen is making can be framed differently, as a deal with living pigs about the continuance of their species. We thus might ask living farm pigs this question: would you prefer that your spot as a species in the farmyard be taken by sheep instead? The pigs cannot of course answer this, but if the only reason that either they or the sheep exist as a species is as a food source for humans, then they would probably prefer the themselves to sheep, and thus appreciate the tacit alliance that we have with them. This rationale could not be paralleled with human slavery. For, the issue with animals involves a reciprocal dependence of two distinct species that already exists within nature (pigs and humans), whereas slavery involves a conflict between members of the same species. Thus, when we look at the success of the pig species, the pigs have no cause to complain on that count.

             The second criticism is that, while the tacit alliance blocks any human sympathy for the pig species, we will still be sympathetic to the individual pigs who are slaughtered. Look again at the wording of Stephen’s argument: “Of all arguments for vegetarianism, none is so weak as the argument from humanity. The pig has a stronger interest than any one in the demand for bacon.” Pig species are indeed well protected by the alliance, so he is right that their species needs no sympathy. In fact, they are so well protected that they carve into the environmental territory of other animals and limit their numbers, to the point of endangerment or extinction. Thus, far from having sympathy for their species, we might even have an annoyance with its success. However, the sense of sympathy is directed as much towards a suffering individual as it is about a suffering species. When we look at the fate of individual pigs, we may certainly feel sympathy for them as they are led to the slaughterhouse as a condition of the alliance. Out of sympathy for that individual pig, we may thus even seek to discontinue that alliance to end the slaughter.


Replaceability Argument for Eating Animals

The third argument for meat eating is that of replaceability, and is best expressed in the words of Peter Singer who developed it: “if we kill one animal, we can replace it with another as long as that other will lead a life as pleasant as the one killed would have led, if it had been allowed to go on living” (Practical Ethics, 2011). If a farm chicken is treated well during its short life and, after being slaughtered, its spot in the farm is taken up by another well-treated chicken, then there was no loss in total happiness by killing the first chicken. Singer explains the underlying rationale:


It is as if sentient beings are receptacles of something valuable, and it does not matter if a receptacle gets broken so long as there is another receptacle to which the contents can be transferred without any getting spilt.


The question here is whether sentient creatures really are merely containers that hold some value, such as happiness, where the happiness itself is more important than the container. I as a human being may object that my worth consists of more than the fleeting moments of happiness that I experience. I have a personal history and future that are part of my identity, and if I die that identity dies with me. Even if my spot on the planet is filled by another human being, that person’s happiness will be no substitute for the value of my life. Don’t just take my word for it, go to my funeral and ask my grieving family and friends if they are consoled by the fact that my place on this planet will be filled by another human being. The replaceability argument, then, does not work very well for humans, and, if higher animals like chimpanzees also have a sense of identity that extends through time, then it will not work well for them either. So too with cows and pigs if their conceptions of personal identity are also at that high level, which they seem to be. Singer acknowledges this much.

             However, Singer argues, some farm animals, such as chickens, may have less sophisticated conceptions of personal identity and may not be much more than containers of happiness, where their transitory experiences of happiness are what is valuable, and not the particular chickens themselves. In that case, so long as we replace one chicken after another in the farmyard, there will be no loss of total happiness by killing each after an allotted time, assuming that each is happy while alive.

             If we then restrict the replaceability argument to lower animals like chickens, might that justify raising and killing them for food? Even with this restriction, the main assumption behind Singer’s replaceability argument is questionable, namely, that we should maximize total happiness “even if the best way to do so is to bring into existence sentient beings who would not otherwise have existed.” Embedded in this is an assumption that, all other factors equal, more is better, and two happy beings are better than one. Let’s suppose that we could manufacture a microcomputer that had the same level of consciousness and happiness as a chicken, but nothing more. It would not be a robot and would not interact with the world, and its entire function would be simply to consciously experience happiness. Based on Singer’s assumption, the more of these microcomputers that we create, the better the world would be, assuming that by creating them we did not cause harm elsewhere. We would need to mass produce them as rapidly as possible, build mountains out of them, and, once earth was comfortably filled with them, perpetually shoot them into outer space. Maybe the universe would be a better place if it was humming everywhere with happy microcomputers, but it is not obvious that it would be, and that is the problem. It is a conjecture that total happiness can be maximized quantitatively by bringing such new happy beings into existence. An alternative and equally plausible conjecture is that total happiness can be maximized qualitatively by simply enhancing the happiness of conscious beings during their normal lives, without substituting their lives with new ones. In the case of chickens, maybe total happiness is maximized by not cutting short the life of one chicken and replacing it with another, but rather by just letting the first chicken live for the duration of its natural life span. The point is that the replaceability argument is no longer a proof for the moral permissibility of killing chickens for food, but, instead, only an argument that it might not be wrong. If there is a moral question about which conjecture is preferable, it must again be settled some other way.




As with most countries around the world, in the U.S. animals have the legal status of property, and have no direct legal standing in their own right as legal persons, the way, for example, that individual people or corporations do. With much of the property we own, such as refrigerators and can openers, we can do with them as we please. Our treatment of the animals we own, though, is regulated by law, some federal, and some state. While many of the laws attempt to safeguard the wellbeing of animals, much of the time they strike a middle ground between the interests of the animals and the financial interests of the owners, such as factory farms, research labs and pet owners. Activist groups that seek to improve the laws protecting animals can be of either the animal welfare and animal rights variety. Animal welfare advocates seek to maintain the legal status of animals as property and their current uses as food and in research, while encouraging reforms on behalf of animals. By contrast, animal rights advocates seek legal personhood status for animals, which would have the practical effect of enabling animal advocacy groups to sue to protect the interests of animals directly.


Federal Animal Laws

U.S. laws that govern the use of animals exist on both the federal level, applying to the nation at large, and the state level, applying to just those jurisdictions. Three federal laws are particularly noteworthy. First, the Humane Methods of Livestock Slaughter Act, enacted in 1958, regulates how animals can be killed for food, with the aim of preventing the needless suffering of animals and also to improve working conditions for people in the slaughtering industry. The heart of the act is its description of how livestock are to be killed: “all animals are rendered insensible to pain by a single blow or gunshot or an electrical, chemical or other means that is rapid and effective, before being shackled, hoisted, thrown, cast, or cut.” Over the years the Act has been criticized on several grounds. First, for decades there was poor enforcement of the laws since inspectors often did not have legal access to the killing floors within the slaughterhouses themselves. Without the ability to directly view the procedures, they could not detect violations. Congress has subsequently attempted to address this deficiency by enacting resolutions that would ensure the enforcement of the slaughter act. Second, the Act focuses only on how agricultural animals are put to death, not on how they are raised, and, as animal rights advocates charge, animals endure widespread suffering and neglect in overcrowded factory farm settings. Third, the Act pertains to only cattle, pigs, and sheep, but not other animals commonly slaughtered, particularly chicken, turkey, and fish, which together comprise over 99% of the animals killed for food in the U.S.

             The second law is the Animal Welfare Act, signed into law in 1966, which aims to protect animals used in scientific research by restricting the procedures that can be performed on them. The Act is accompanied by a detailed and regularly updated set of regulations that provide guidelines for researchers. The regulations that pertain directly to animal pain during experiments are the following:


(i) Procedures involving animals will avoid or minimize discomfort, distress, and pain to the animals . . . (iii) The principal investigator has provided written assurance that the activities do not unnecessarily duplicate previous experiments; (iv) Procedures that may cause more than momentary or slight pain or distress to the animals will: (A) Be performed with appropriate sedatives, analgesics or anesthetics, unless withholding such agents is justified for scientific reasons, in writing, by the principal investigator and will continue for only the necessary period of time. . . (v) Animals that would otherwise experience severe or chronic pain or distress that cannot be relieved will be painlessly euthanized at the end of the procedure or, if appropriate, during the procedure; (vi) The animals' living conditions will be appropriate for their species . . . and contribute to their health and comfort. [AWA Code of Federal Regulations, 2.31]


The guidelines above attempt to address many of the concerns of animal rights advocates, such as minimizing suffering, avoiding duplication, providing adequate care and living conditions. However, a weakness of the guidelines is that there is great latitude within them that allow researchers to perform painful experiments on conscious animals, and the minimum standards set for adequate care and living conditions may be too low.

             The third law is the Animal Enterprise Terrorism Act (2006), which aims to protect companies from vandalism by animal activist groups. A similar law was enacted in 1992, called the Animal Enterprise Protection Act, but animal research and agricultural companies successfully lobbied Congress to strengthen the law and classify offenders as terrorists. The law specifically targets any action that “intentionally damages or causes the loss of any real or personal property (including animals or records) used by an animal enterprise, or any real or personal property of a person or entity having a connection to, relationship with, or transactions with an animal enterprise.” While the law is primarily geared to punish animal activists who cause property damage, its broad wording could be applied to non-violent protestors if their activities result in a loss of profits. Opponents of the Act charge that this undermines animal activists’ legitimate right to protest against mistreatment of animals, as one critic states here:


That clause, “loss of profits,” would sweep in not only property crimes, but legal activity like protests, boycotts, investigations, media campaigning, and whistleblowing. It would also include campaigns of non-violent civil disobedience, like blocking entrances to a laboratory where controversial animal testing is taking place. Those aren't acts of terrorism. They are effective activism. Businesses exist to make money, and if activists want to change a business practice, they must make that practice unprofitable. [William Potter, U.S. House Judiciary subcommittee hearing, Animal Enterprise Terrorism Act (2006)]


             Other federal animal laws deal with the creation of wildlife management programs, protection of marine mammals and migratory birds, and prohibitions against animal fighting. One federal law, the “Companion Animals Federal Pet Protection Act” (2010, 7 USC 2158), requires that pet shelters wait a period of five days before selling unclaimed pets. The purpose of the Act, it explains, “is to prevent animals from being stolen and purchased from humane societies in order to use the animals for scientific testing or illegal purposes (such as fighting, etc.).” About 50,000 dogs and 100,000 cats each year are purchased from animal shelters for use in animal testing. The waiting period gives owners a chance to retrieve their lost pets before they might meet with that fate. In spite of this law, pets continue to be stolen by research animal dealers. In one investigation a dealer stated "I know a few boys that go into rich neighborhoods. . . they get some of them rich people's dogs and they don't even know what happened to 'em." Another dealer admitted, "Well, let's face it, it's not legal, you know. I took stolen dogs to him . . . I think well -- that could be a child's dog. You know -- that could be a pet, ya know. . . Hey, a buck's a buck" (U.S. House Agriculture committee hearing, Review of the Welfare of Animals in Agriculture, 2007).


State and International Animal Laws

While federal U.S. animal laws govern many aspects of animal treatment, there is no comprehensive federal law that deals with animal cruelty: each state must enact its own laws, and all 50 states have indeed done so. The state laws are only criminal, and not civil, which means that animal owners—individuals or companies—cannot be sued for cruelty, but only criminally punished. While cruelty to animals can be a felony offense in most states, offenders are most often prosecuted for lesser misdemeanor charges. An example of a state animal cruelty law is the following from California:


every person who maliciously and intentionally maims, mutilates, tortures, or wounds a living animal, or maliciously and intentionally kills an animal, is guilty of an offense punishable by imprisonment in the state prison, or by a fine of not more than twenty thousand dollars ($20,000), or by both the fine and imprisonment, or, alternatively, by imprisonment in a county jail for not more than one year, or by a fine of not more than twenty thousand dollars ($20,000), or by both the fine and imprisonment. . . . Every person [is also guilty of a punishable offense] who overdrives, overloads, drives when overloaded, overworks, tortures, torments, deprives of necessary sustenance, drink, or shelter, cruelly beats, mutilates, or cruelly kills any animal. [California penal code sect. 597]


In addition to the above general law against animal cruelty, California has dozens of more specific laws that regulate animal hunting, fishing, trapping, breeding, training, impounding, poisoning, euthanizing and slaughtering. Some laws are geared towards specific animals, such as those prohibiting the abuse of elephants, dog fighting, or the sale of dog and cat pelts.

             Countries around the world face the same animal-related problems that the U.S., and thus devise their own policies, many of which are more animal-friendly. Germany has granted legal rights to animals. A farm animal welfare organization that advises the British government has devised a list of “five freedoms” for animals:


1. Freedom from Hunger and Thirst—by ready access to fresh water and a diet to maintain full health and vigor.

2. Freedom from Discomfort—by providing an appropriate environment including shelter and a comfortable resting area.

3. Freedom from Pain, Injury or Disease—by prevention or rapid diagnosis and treatment.

4. Freedom to Express Normal Behavior—by providing sufficient space, proper facilities and company of the animal's own kind.

5. Freedom from Fear and Distress—by ensuring conditions and treatment which avoid mental suffering.


Many European countries have adopted a Pet Protection Treaty, which aims to protect pets against unnecessary pain, suffering, distress, and abandonment. But Switzerland has enacted what are perhaps the most animal-friendly laws to date. A 1992 law mandates that animals be recognized as beings, not things, and a more recent 2008 law extends to them a range of unique protections. Social animals, such as hamsters and parrots, cannot be kept in cages by themselves. Fishermen cannot use live bait and are prohibited from catching then releasing fish, essentially fishing for sport rather than food. Live goldfish cannot be flushed down the toilet and owners of aquariums must light them in a way that maintains a natural cycle of day and night. New dog owners are required to take a course on how to best meet the needs of their pets.




The Conservative Position

The conservative position on the topic of the moral status of animals is that humans have a moral standing that is superior to that of animals, which justifies our use of them. Animals have no moral rights— and should have no legal rights—and animal pain is justified when it brings about a human good. The main arguments for the conservative position are these.

             1. Animals are here for our use: As part of the natural order of things, animals exist for human benefit, and we can use them as we see fit. As the dominant species on this planet, all living things are under our complete authority. A criticism of this argument is that might does not make right. Merely having power over something does not entitle one to harm, torture or exploit it. A king can’t line up and shoot his subjects just because he dominates them. We even recognize this with inanimate objects such as national treasures and irreplaceable works of art. If a museum owns the Mona Lisa, that does not give the museum the moral authority to destroy it. So too with animals: dominance over animals in and of itself does not justify us in doing what we want to them.

             2. Animal use is necessary. Use of animals is a matter of human survival, and that surpasses any other consideration we may have towards them. We biologically depend on animals for food, and we culturally depend on animals for scientific advancement and safe consumer products. In a perfect world we might give more consideration to animal interests, but as things stand, our use of them is a necessity. A criticism of this argument is that, while animal use may have been necessary for human survival in previous eras, it is no longer true today. We don’t need animals for food, clothing and labor. We no longer need them for scientific research and consumer product testing. We keep using animals for these purposes since that’s the way we’ve always done it, but that doesn’t mean that it is still necessary.

             3. Human interests have greater importance: Human interests are more important than those of animals, and thus outweigh them. There is a qualitative difference between the lives that humans lead and those that animals do. Unlike animals, we have an appreciation of cultural advancement; we have capacities for art, music, scientific exploration, historical knowledge. Every action we perform as humans is set against this backdrop of superior human interests, which overshadows the more brutish interests of animals. A criticism of this argument is that trivial human interests do not outweigh important animal interests. My desire for a tasty hamburger does not outweigh the interests of a cow to continue to remain alive. My interest in wearing alluring cosmetics does not outweigh the interests of lab animals to be free from painful toxicity tests. I may have the aesthetic capacity to appreciate fancy clothes, but that doesn’t justify me in skinning an animal for that purpose. In most cases, the specific interests that we have when using animals are quite trivial when compared to the animals’ interests to remain alive and not experience pain.


The Liberal Position

The liberal position regarding animals is that many of them have moral worth, and thus qualify for both moral and legal rights. Thus, most human uses of these animals are not morally justified, and animal pain is never justifiable even if it leads to a human good. The main arguments for the liberal position are these.

             1. Some animals are self-aware. Higher animals, such as dogs, cats, pigs, and chimps, have higher mental capacities of self-awareness that give them their own desires, preferences, and sense of identity. This capacity qualifies them for moral worth, which in turn, means that they have rights to pursue their preferences, just as we humans have rights to pursue ours. A criticism of this argument is that few animals have higher mental abilities that compare to those of humans. Maybe the great apes and large sea mammals have brain structures that give them human-like self-awareness, but that might be it. While animals like dogs, cats and pigs have impressive mental abilities, they do not necessarily rise to the level that would give them human-like moral or legal rights.

             2. Many animals are sentient. Vertebrate animals, from fish on up to humans, have nervous systems that enable them to consciously experience pain. This capacity qualifies them for moral worth, and implies that they have the right not to be inflicted with pain. Virtually all of the uses that we make of animals—for food, clothing, research, entertainment—subjects animals to pain, and is thus unjustifiable. A criticism of this argument is that not all vertebrates perceive pain in the same way, and how they do depends on the size and structure of their brains. Compare, for example, the level of conscious sentience of a minnow fish with that of a chimp. The two may be so far apart that, even if we granted moral worth to a chimp, the minnow’s sentience might be to too insubstantial to warrant it having moral worth. Thus, if there is no uniform experience of sentience from one creature to another, then there is no uniform standard of moral worth which they all have.

             3. Humans are traditionally speciesists. We have a longstanding bias in favor of our own species, which prevents us from seeing the moral worth of animals. Throughout history we’ve defined notions of rationality, personal identity, dignity, and moral worth in terms of our human experience. We’ve largely ignored the sophisticated capacities of animals to communicate with each other and solve problems. The more we learn about animals, though, the more we can see important cognitive similarities with those of humans. The traditional bias that we’ve had against the moral status of animals is grounded in ignorance and unfounded stereotypes, in much the way that racial and gender bias are. A criticism of this argument is that we have good reason to view species differently, but no good reason to view races and genders differently. For example, there are no dissimilarities with the cognitive abilities of races, which thus makes racial bias unjustified. But even our most impartial understanding of animals reveals enormous gaps between their cognitive abilities and ours, which justifies us in giving them a different status.


A Middle Position

Throughout the animal rights debate, it is easy to find areas of compromise on both sides. On the one hand, we know so much more about animal physiology and cognition now than in previous centuries that the traditional clear-line distinction between the moral worth of animals and humans must be rejected. On the other hand, science tells us that there are significant differences between the cognitive abilities of animals and humans, and even between animals themselves; thus, it seems untenable to hold that humans and all animals have equal moral worth. The sliding scale position on the moral worth of animals is a reasonable compromise, and it has the benefit of relying directly on what science tells us about the differing cognitive capacities of animals. The greater is their capacity for sentience and self-awareness, the greater is their moral worth. The challenge, though, is altering animal laws and business practices in ways that would reflect the differing degrees of moral worth of animals. It would be easy enough to accept the Great Ape Declaration, as New Zealand already has. It would also be easy enough to at least cut back on animal testing in the ways suggested by the Three Rs of humane animal experimentation. Meat consumption could be dramatically reduced, even if only for reasons of health, and factory farming techniques could be eliminated, as some European countries are doing. Other areas of animal welfare, though, may be more difficult to regulate—such as with hunting, fishing and pet ownership—and may require time for society to acclimate to animal-friendly restrictions.




Please answer all of the following questions.


1. What are the four mechanisms involved in the human perception of pain?

2. What are some of the problems associated with factory farming?

3. What are the three purposes of animal testing and the three Rs of animal testing?

4. What is Descartes’ clear line position on the status of animals?

5. What is Pythagoras’s equality position on the status of animals?

6. What is Darwin’s sliding scale position on the status of animals?

7. What are the five positions on indirect duties to animals?

8. What is Nozick’s criticism of indirect duties to animals?

9. What are the two main points of Singer’s sentience view of animals?

10. What is Wertheimer’s defense of speciesism?

11. What are the two main points of Regan’s view of animal rights?

12. What is Cohen’s criticism of Regan?

13. What is Aquinas’s natural order argument for eating animals, and what is Plutarch’s opposing view?

14. What is Stephen’s tacit alliance argument for eating animals and Salt’s criticism of it?

15. What is Singer’s replaceability argument for eating animals and the criticism of it in the text?

16. What are the three main federal laws regarding animals?

17. What are the criticisms of the Humane Methods of Livestock Slaughter Act?

18. What are the five freedoms of animals endorsed by the British?

19. What are the criticisms of the three conservative arguments regarding animals?

20. What are the criticisms of the three liberal arguments regarding animals?

[Short Essay]

21. Short essay: pick any one of the following views in this chapter and criticize it in a minimum of 150 words. The position of Descartes, Pythagoras, Darwin regarding animals; one of the five positions on indirect duties to animals; Singer’s or Wertheimer’s view of speciesism; Regan or Cohen’s view of animal rights, the view of meat eating by Aquinas, Plutarch, Stephen, or Singer.