Conversations regarding the ethics of eating meat are focused on whether or not it is moral to eat non-human animals. People who abstain from eating meat are generally known as vegetarians and people who avoid all animal by-products are known as vegans. They avoid meat for a variety of reasons, including taste preference, animal welfare, ethical reasons, religion, the environmental impact of meat production (environmental vegetarianism), health considerations,[1] and antimicrobial resistance.[2] Individuals who promote meat consumption do so for a number of reasons, such as health, cultural traditions, religious beliefs,[3] and scientific arguments that support the practice.[4][5] The majority of the world’s health and dietetics associations state that a well-planned vegetarian or vegan diet can be nutritionally adequate for all stages of life.

A common argument used in the animal rights movement is the argument from marginal cases, asserting that non-human animals should have the moral status similar to that of marginal case human beings such as human infants, the senile, the comatose, and the cognitively disabled. Proponents argue that there are no morally relevant traits that these marginal humans possess that animals lack.

In addition to flesh, vegans also abstain from other animal products, such as dairy products, honey and eggs, for similar reasons. "Ethical omnivores" are individuals who object to the practices underlying the production of meat, as opposed to the act of consuming meat itself. They do not believe animals deserve the right not to be killed and treated as commodities, but rather, they believe it is permissible to kill them as long as welfare is taken into account. In this respect, many people who abstain from certain kinds of meat eating and animal products do not take issue with meat consumption in general, provided that the meat and animal products are produced in a specific manner.[6] Ethical omnivores may object to rearing animals for meat in factory farms, killing animals in ways that cause pain, and feeding animals unnecessary antibiotics or hormones. To this end, they may avoid meats such as veal, foie gras, meat from animals that were not free range, animals that were fed antibiotics or hormones, etc.[7]

In a 2014 survey of 406 US philosophy professors, approximately 60% of ethicists and 45% of non-ethicist philosophers said it was at least somewhat "morally bad" to eat meat from mammals.[8] A 2020 survey of 1,812 published English-language philosophers found that 48% said it was permissible to eat animals in ordinary circumstances, while 45% said it was not.[9] The World Scientists' Warning to Humanity (2017), the most co-signed scientific journal article in history, called (among other things) for a transition to plant-based diets in order to combat climate change.[10]

Overview of arguments for and against meat eating

Cattle carcasses in a slaughterhouse[11]

Conversations regarding the ethics of meat eating have been ongoing for thousands of years, possibly longer. Pythagoras, a Greek mathematician and philosopher who lived during the 6th century BC, made the case against eating animals on grounds of their having souls like humans. Taking an entirely different approach, Plato, an Athenian philosopher who lived during the 4th century BC, argued that meat is a luxury item that requires a lot of land to procure. As a result, he stated that the unmoderated consumption of meat would lead to conflict over land and, ultimately, an unsustainable society.[12] Xenophon expressed similar concerns to Plato:[13][14]

Plutarch, a Middle Platonist philosopher and vegetarian, dedicated a section of his Moralia to the consumption of animals. He argued that flesh-eating is not a necessity but a luxury rooted in gluttony and desensitization to violence. He emphasized the cruelty of killing animals for pleasure, contrasting it with the simplicity and sufficiency of plant-based sustenance. Furthermore, Plutarch argued that, since there was a possibility that souls could migrate from human bodies to animal bodies after death, that human and animal lives should be beholden to the same standard of care:[15]

"Kill it! It's only a brute beast"; but the other says, "Stop! What if the soul of some relative or friend has found its way into this body?" — Good God! Of course the risk is equal or much the same in the two cases — if I refuse to eat flesh, or if I, disbelieving, kill my child or some other relative!"

Rene Descartes, a 17th-century French philosopher, mathematician, and scientist, disagreed with the aforementioned stances. He argued that animals were not conscious. As a result, he asserted that there is nothing ethically wrong with consuming meat or causing animals physical pain. Immanuel Kant also argued that there is nothing ethically wrong with meat consumption. He claimed that it was personhood that distinguished humans from animals and that, since animals are not actual persons, there was nothing wrong with killing or consuming them.[12]

Peter Singer, a Princeton University and University of Melbourne professor and pioneer of the animal liberation movement, argues that, because non-human animals feel, they should be treated according to utilitarian ethics. In his ethical philosophy of what it is to be a "person", Singer ultimately argues that livestock animals feel enough to deserve better treatment than they receive. Singer's work has since been widely built upon by philosophers who agree[17] and who do not.[18] His essential philosophies have been largely adopted by animal rights advocates[19] as well as by ethical vegetarians and vegans.

Many other modern thinkers have questioned the morality not only of the double standard underlying speciesism but also the double standard underlying the fact that people support treatment of cows, pigs, and chickens in ways that they would never allow with pet dogs, cats, or birds.[17]

Nick Zangwill, a British philosopher and honorary research professor at University College London and Lincoln University, disagrees with Singer's conclusions about the moral necessity of not eating meat. In Our Moral Duty to Eat Meat, which was published by Cambridge University Press, Zangwill argues that the existence of domesticated animals depends on the practice of eating them, and that meat eating has historically benefitted many millions of animals and given them good lives. Consequently, he claims that eating non-human animal meat is not merely permissible but also good for many millions of animals. However, Zangwill clarifies that this argument does not apply to factory farm animals, as they do not have good lives. Thus, when he speaks of meat eating being justified, he means only meat from animals that overall have a good life.[20] Proponents of meat eating who subscribe to Zangwill's views argue that practices like well-managed free-range rearing and the consumption of hunted animals, particularly from species whose natural predators have been significantly eliminated, could satisfy the demand for mass-produced, ethically sourced meat.[21]

Ethical vegetarians say that the reasons for not hurting or killing animals are similar to the reasons for not hurting or killing humans. They argue that killing an animal, like killing a human, can only be justified in extreme circumstances, such as when one's life is threatened. Consuming a living creature just for its taste, for convenience, or out of habit is not justifiable. Some ethicists have added that humans, unlike other animals, are morally conscious of their behavior and have a choice; this is why there are laws governing human behavior, and why it is subject to moral standards.[22] Ethical vegetarian concerns have become more widespread in developed countries, particularly because of the spread of factory farming, more open and graphic documentation of what human meat-eating entails for the animal,[23] and environmental consciousness. Reducing the worldwide massive food waste would also contribute to reduce meat waste and therefore save animals.[24][25]

Some have described unequal treatment of humans and animals as a form of speciesism such as anthropocentrism or human-centeredness. Val Plumwood (1993, 1996) has argued that anthropocentrism plays a role in green theory that is analogous to androcentrism in feminist theory and ethnocentrism in anti-racist theory. Plumwood calls human-centredness "anthropocentrism" to emphasize this parallel. By analogy with racism and sexism, Melanie Joy has dubbed meat-eating "carnism". The animal rights movement seeks an end to the rigid moral and legal distinction drawn between human and non-human animals, an end to the status of animals as property, and an end to their use in the research, food, clothing, and entertainment industries.[26][27]