Veganism 101: An Introduction

Before the Word “Vegan” (proto-veganism)

Note: We refer to proto-veganism as the early historical or cultural practices, philosophies, or diets that resemble or anticipate modern veganism, even if they predate the formal term “vegan.”

The word “vegan” may be relatively new, but the idea isn’t. Veganism is just one point on a historical continuum of human concern for other animals. 

Long before factory farming, and long before the word “vegan,” prominent historical figures saw that exploiting animals requires animal suffering, and they embodied vegan ethics in their writings and actions. 

Pythagoras (570–495 BCE)

• Pythagoras, an influential Greek philosopher and mathematician, invented the word “philosophy,” first called the universe the “cosmos,” and first used the word “theory” the way it’s used. He’s perhaps best known for the Pythagorean Theorem.¹
• Pythagoras believed humans and animals have a special kinship. He refused to eat animals not because of their intelligence but because of their capacity to feel pleasure and pain.²
• Pythagoras had followers known as Pythagoreans. Until the 19th century, when the word “vegetarian” came into use, the Pythagorean diet meant what “vegetarian” means now.³

Leonardo da Vinci (1452–1519)

• Leonardo da Vinci was a quintessential Renaissance polymath, renowned for his mastery of art, science, engineering, and painting. Da Vinci was ahead of his time, not only in designing bicycles, airplanes, and helicopters but also in his attitude toward animals. According to one biographer, he was “a man imbued with an uncommon compassion for all living things.”⁴
• Leonardo da Vinci said he would not let his body become “a tomb for other animals, an inn of the dead…”⁵ He loved animals, refused to eat them, and abhorred the thought of hurting them.⁶
• In the open markets of Florence, Leonardo da Vinci frequently bought caged birds just to release them, giving back their freedom.⁷

Percy Bysshe Shelley (1792–1822)

• Shelley was a major English Romantic poet known for his lyrical poetry. His works, including “Ozymandias,” “Prometheus Unbound,” and “To a Skylark,” reflect his passion for political and social reform, as well as exploring nature and the human condition. Shelley’s idealism and imaginative style helped shape future literary movements. 
  
• Shelley, who one biographer calls the first celebrity vegan,⁸ regretted that “beings capable of the gentlest and most admirable sympathies, should take delight in the death-pangs and last convulsions of dying animals.”⁹
• He wrote a book, A Vindication of Natural Diet, which uses comparative anatomy to show that vegetable diets suit humans best.¹⁰

Leo Tolstoy (1828–1910)

• Leo Tolstoy was a Russian novelist, philosopher, and social reformer, best known for his epic novels War and Peace and Anna Karenina, which explore complex themes of history, morality, and the human experience. He is a leading figure in realist literature and one of the most important literary and philosophical minds of the 19th century.
• Tolstoy wrote a book titled The First Step: An Essay on the Morals of Diet, which called abstaining from animal foods the first step toward moral perfection.¹¹
• He says using animal foods “is simply immoral, as it involves the performance of an act which is contrary to the moral feeling—killing; and is called forth only by greediness and the desire for tasty food.¹²
• He also condemns self-delusion, saying, “we are not ostriches, and cannot believe that if we refuse to look at what we do not wish to see it will not exist.”¹³

George Bernard Shaw (1856–1950)

• George Bernard Shaw was an Irish playwright, critic, and polemic, renowned for his sharp wit and social commentary. His plays, such as Pygmalion, tackle issues such as class, feminism, and religion. He was awarded the Nobel Prize in Literature in 1925.
• Shaw was one of many to connect animal slaughter to the lack of world peace, saying, “While we ourselves are the living graves of murdered beasts, how can we expect any ideal conditions on this earth?”¹⁴
• Shaw is credited with the famous quote, “Animals are my friends…and I don’t eat my friends.”¹⁵

Mahatma Gandhi (1869–1948)

• Mahatma Gandhi led India’s nonviolent struggle for independence from British rule. He developed and popularized nonviolent resistance, which inspired civil rights movements worldwide—and leaders like Martin Luther King Jr. and Nelson Mandela.
• Gandhi believed “the more helpless a creature, the more entitled it is to protection by man from the cruelty of man.”¹⁶
• As a young law student in London, he made spreading vegetarianism (the animal ethics standard of the time) his mission,¹⁷ and he carried out that mission by writing essays and giving speeches.¹⁸
• It seems he honed his activism skills by being a voice for animals and then used those skills to change the course of human history.

The Birth of a Movement

Donald Watson coined the word “vegan” in 1944, before Watson and others founded the Vegan Society. “Vegan” was formed using the first three letters and last two letters of the word “vegetarian.”¹⁹

Watson was unhappy that “vegetarian” had morphed to include dairy, and he thought a new word for “non-dairy vegetarian” was needed.²⁰

The Vegan Society’s definition of “veganism” changed over the years, but by 1988, it settled as the one most cited today: “a philosophy and way of living which seeks to exclude—as far as possible and practicable—all forms of exploitation of, and cruelty to, animals for food, clothing, or any other purpose.”²¹

This first issue of the Vegan Society newsletter was published in November, 1944.²² The Vegan Society is still active today.²³

In the first issue of the Vegan Society newsletter, Watson predicted humankind would eventually “view with abhorrence the idea that men once fed on the products of animals’ bodies.”²⁴

Note: See our briefing “Animal Agriculture: Cruel and Unjust” for more details, or our even more focused briefings on cows, pigs, chickens, and fish. Future briefings will address the exploitation of animals in entertainment, clothing, sport, and research.

Slaughter is unjust even if done suddenly and painlessly (which it is not).

Slaughter, even if sudden and painless, is unjust because it deprives an individual of their future experiences, choices, and right to live.

Life has inherent value, and ending it disregards the moral worth of the being, regardless of the method.

The harm of killing goes beyond physical suffering; it is the fundamental injustice of taking away a life that is valued and could have continued.

Because we have no nutritional need for meat, dairy, or eggs, the deaths those products require are unnecessary, as is the suffering.

Exploited animals suffer many abuses.

Below is just a sample of the abuses farmed animals face—abuses that also cause stress, depression, and poor mental health.²⁵

Violent Slaughter: Shooting | Maceration | Throat Slitting

• Slaughter methods such as throat slitting, shooting, maceration, electrocution, and gassing inflict extreme suffering, often causing prolonged pain, suffocation, internal burning, or severe bodily trauma due to ineffective stunning and high-speed processing.^{2627282930313233}

Horrid Living Conditions: Confinement | Crowding | Fecal Filth

• Farm animals endure extreme confinement, standing in waste-filled enclosures, packed so tightly they cannot move, and suffer from respiratory issues, oxygen deprivation, and disease due to overcrowding and unsanitary conditions.^343536373839

Painful Mutilations: Debeaking | Dehorning | Tail Docking | Castration

• Farm animals undergo painful mutilations, including beak trimming, castration, tail docking, ear notching, and dehorning, often without anesthetic or pain relief.^{4041 424344454647}

Denial of Natural Behaviors: Free Movement | Courtship | Sex | Roosting | Rooting | Nurturing and Being Nurtured | Playing | Teaching

• Farm animals are often separated from their offspring, causing distress and long-term anxiety, while extreme crowding prevents natural behaviors, leading to constant fear and stress..^484950515253

Debilitating Selective Breeding: Larger Breasts | More Milk | More & Bigger Eggs

• Farm animals are bred for more and larger eggs, larger breasts, excessive milk, and more muscle, causing osteoporosis, broken bones, uterine prolapse, deformities, heart attacks, metabolic diseases, and high mortality rates.^{5455565758596061}

Reproductive Violations: Semen Collection | Insemination | Separation of Offspring

• Farm animals endure painful semen collection through electro-ejaculation or forced mounting, while artificial insemination involves invasive procedures that require manual penetration and cause significant stress and discomfort.⁶²⁶³⁶⁴

Cruel Handling: Beating | Prodding | Transportation | Maceration | Slaughter

• Farm animals suffer violent handling during transport and confinement, often grabbed, thrown, and crammed into crowded spaces, leading to broken bones, suffocation, and severe injuries. Many endure beatings, kicks, and other physical abuse, causing pain, fear, and lasting harm.^6566676869

Downers: Dragging | Electrocution | Forklifting | Spraying | Left to Die

• Farm animals who are too weak or injured to stand are often denied veterinary care, beaten, dragged, electrocuted, rammed with forklifts, or simply left to die.^70717273

Farmed animals are slaughtered very young, after living only a fraction of their natural lifespans.

Animals slaughtered for meat live only 2%–7% of their natural lifespan, laying hens live less than 20% of their natural lifespan, and dairy cows live 30% of their natural lifespan.^747576777879

Humane-sounding labels and certifications are deceptive and largely meaningless.

Humane labels and certifications are a form of humane washing, deceiving consumers by portraying animal products as ethical while hiding the reality of suffering. Investigations by Consumer Reports and the Open Philanthropy Project found that terms like cage-free, free-range, and pasture-raised are largely meaningless, with audits that are infrequent, ineffective, and rarely enforced.^80818283

Even the highest-tier certifications allow for extreme confinement, lack of exercise and socialization, genetic modifications that cause health issues, and routine practices such as separating calves from their mothers and mass-killing male chicks.”⁸⁴

The scope of suffering, as indicated by the numbers slaughtered, is beyond imagination.

The scale of suffering is immense, with over 70 billion land animals slaughtered each year (FAO⁸⁵)—99% from factory farms(Sentience⁸⁶). The yearly toll exceeds the total number of humans who have ever lived.

Calculation Details

Public Broadcasting Radio estimates that as of 2022, the total number of humans who have ever lived on Earth is 117 billion.⁸⁷

Annually, over 70 billion land animals⁸⁸ and 51 to 167 billion fish⁸⁹ are slaughtered.

The root of the problem is viewing animals as mere things with no inherent worth—that exist only for humans and for maximizing profit.

Industry publications openly depict farm animals as machines, such as those stating that pigs should be treated like factory equipment and that sows’ purpose is “to pump out baby pigs like a sausage machine.”⁹⁰⁹¹

Note: See our briefing titled “Vegan Diets Can Be Healthy and Protective Against Chronic Disease” for a more detailed look at vegan diets.

Prominent health organizations embrace a vegan diet.

Mayo Clinic,⁹² Harvard Public Health,⁹³ Cleveland Clinic,⁹⁴ Kaiser Permanente,⁹⁵ NewYork-Presbyterian,⁹⁶ and others have all said plant-based diets are not only sufficient but also promote health and help prevent chronic diseases such as heart disease, diabetes, high blood pressure, obesity, and high cholesterol.

Cleveland Clinic said, “There really are no disadvantages to a herbivorous diet!” and “Obtaining proper nutrients from non-animal sources is simple for the modern herbivore.”⁹⁷

Kaiser Permanente even advises their doctors to recommend a plant-based diet to their patients, especially those with high blood pressure, diabetes, cardiovascular disease, or obesity.⁹⁸

Dietetic associations endorse a vegan diet.

The Academy of Nutrition and Dietetics is the largest nutrition-focused organization in the world, with over 100,000 credentialed professionals.⁹⁹ Their 2025 formal position statement endorses well-planned vegan diets as healthy and nutritionally adequate for adults, and says that “…vegan dietary patterns can be recommended by RDNs [Registered Dietitian Nutritionists], when appropriate, for prevention and management of some chronic diseases.”¹⁰⁰

The dietetic associations of other countries, including Canada,¹⁰¹ England,¹⁰² and Australia,¹⁰³ have made similar statements.

Various plant-based initiatives have shown excellent results.

Plant Pure Nation

The Plant Pure Nation initiative went into various rural communities and fed people veganized versions of standard dishes.¹⁰⁴

Participants experienced significant improvements in key health markers, such as reductions in cholesterol levels, blood pressure, blood sugar, triglycerides, and body weight. Many reported better energy levels and a decrease in reliance on medications.¹⁰⁵

The Ornish Reversal Program

Dr. Ornish’s program¹⁰⁶ has been implemented in numerous hospitals and is approved by Medicare.¹⁰⁷

It is the only program scientifically proven in randomized controlled trials to reverse the progression of even severe coronary heart disease without drugs or surgery.¹⁰⁸

All essential nutrients can be obtained without consuming animal products.

When major health organizations, research institutions, and dietetic associations all say we have no nutritional need for animal products, we’ve reached a scientific consensus.

Note: See our briefing titled “The Environmental Impact of Animal Agriculture” for a more detailed look at animal agriculture’s environmental impacts. 

Scientists agree animal agriculture is a major driver of environmental destruction.

The United Nations Environment Program (UNEP) called meat the “world’s most urgent problem” and said, “our use of animals as a food-production technology has brought us to the verge of catastrophe.”¹⁰⁹

The Worldwatch Institute said, “The human appetite for animal flesh is a driving force behind virtually every major category of environmental damage now threatening the human future.¹¹⁰

An article in Georgetown Environmental Law Review sums it up nicely, calling animal agriculture the “one industry that is destroying our planet and our ability to thrive on it.”¹¹¹

Vegan diets have the smallest environmental footprint.

An analysis using data from the United States Department of Agriculture (USDA) determined that vegan diets have roughly half the environmental footprint of a meat-centric diet and 60% the footprint of the average American diet.¹¹²

Findings published in the journal Nature Food in 2023 showed that plant-based diets, compared to meat-rich diets…¹¹³

• produce ~75% fewer greenhouse gas emissions.
• use ~54% less water.
• use ~75% less land.

Animal agriculture’s devastation is far-reaching.

Livestock or animal agriculture’s contribution to global warming varies from 14.5% to 87% depending on the assumptions made. The higher numbers include the lost opportunity cost of carbon sequestration through reforestation, which is reasonable to include.

Animal agriculture is not only a leading cause of global warming but also contributes greatly to habitat destruction, deforestation, water waste, water and air pollution, biodiversity loss, desertification, ocean dead zones, and fecal contamination.¹¹⁴

Animal agriculture is responsible for 80% to 90% of Amazon rainforest destruction (Yale¹¹⁵ and World Bank¹¹⁶).

Livestock overgrazing is the single greatest cause of desertification worldwide, according to a study published in the Annual Review of Environment and Resources.¹¹⁷

According to a 2023 study published in Nature Communications, reduced air pollution due to plant-based diets could save over 200,000 human lives per year.¹¹⁸

Biomass research puts animal agriculture’s dominance of the planet in perspective.

A 2018 study titled “The biomass distribution on Earth” published in the Proceedings of the National Academy of Sciences (PNAS), as analyzed by Our World in Data, revealed the following:¹¹⁹

• Of all the mammal biomass on Earth, 62% is farm animals, 34% is humans, and 4% is wild animals.
• The total weight of chickens on farms is approximately 2.5 times the total weight of all wild birds.
• Humans and livestock combined outweigh wild mammals by about 24 to 1.

Animal agriculture’s environmental harm stems from its inefficiency.

Animal agriculture is so inefficient because most of the calories farmed animals consume go toward the animals’ daily living. Also, some calories they consume go toward growing body parts that are not consumed (Applied Animal Nutrition Journal¹²⁰).

On average, it takes 24 calories of plant-based feed to produce 1 calorie of animal-based food (World Resources Institute, “Creating a Sustainable Food Future”¹²¹).

Animal agriculture uses 83% of global farmland while producing only 18% of the total calories and 37% of the protein calories that humans consume (2018 study from Oxford¹²²).

Reducing animal agriculture is crucial.

The United Nations Environment Program (UNEP) said, “A substantial reduction of [harmful environmental] impacts would only be possible with a substantial worldwide diet change, away from animal products.”¹²³

Sir David Attenborough, broadcaster and naturalist, said,
“We must change our diet. The planet can’t support billions of meat-eaters.”¹²⁴

Veganism is a social justice movement in two significant ways. The first concerns how human injustices arise from using animals for food; the second concerns its commonalities with all forms of oppression.

Human social injustices arising from using animals for food production.

Animal agriculture leads to food sequestering and shortages, while veganism does the opposite—mitigating global hunger and starvation—as shown in our briefing on the topic.

Climate change, in which animal agriculture plays a significant role, disproportionately affects the poor, as they are more vulnerable to natural disasters, crop yield losses, and other tragedies.¹²⁵

Slaughterhouse workers suffer from high rates of injuries, infections, illnesses, and PITS (Perpetration-Induced Traumatic Stress), a form of PTSD¹²⁶

Rates of violent crime, including domestic abuse and rape, are higher in communities near slaughterhouses.¹²⁷

One example of animal agriculture’s environmental injustice comes from North Carolina, where the feces and urine of 9.5 million swine from over 2,000 high-density farms is stored in open-air cesspools. Due to this inadequate storage, the waste is sprayed into fields and drifts into the yards and homes of the poor community nearby. This results in not only foul odors but also asthma attacks, bronchitis, and runny noses and eyes.¹²⁸ After decades, the problem still persists.¹²⁹

Social justice is anti-oppression.

Veganism has been recognized as a social justice movement since the movement’s beginning in 1944.

• In the first issue of the Vegan Society newsletter, The Vegan News, Watson says, “We can see quite plainly that our present civilization is built on the exploitation of animals, just as past civilizations were built on the exploitation of slaves…”¹³⁰

The various forms of oppression, whether of humans or animals, share common mechanisms and structures. All forms of oppression use power dynamics, social hierarchies, and cultural norms to objectify, dehumanize, hurt, and control.¹³¹¹³²

A. Breeze Harper (aka Sistah Vegan), Carol Adams, and other ecofeminists have written extensively on how various forms of oppression are connected.¹³³¹³⁴

Joaquin Phoenix, during his Academy Award acceptance speech in 2020, summarized this connection:

• “I see commonality. Whether we’re talking about gender inequality or racism or queer rights or indigenous rights or animal rights, we’re talking about the fight against injustice. We’re talking about the fight against the belief that one nation, one people, one race, one gender or one species has the right to dominate, control and use and exploit another with impunity.”¹³⁵

The Deontological Rights-Based Approach

Tom Regan, in his book The Case for Animal Rights (1983), argues that animals are “subjects of a life” and thus possess inherent value, making animal exploitation morally impermissible, regardless of the circumstances.¹³⁶

Tom Regan says, “The philosophy of animal rights stands for, not against, justice. We are not to violate the rights of the few so that the many might benefit. Slavery allows this, child labor allows this, all unjust social institutions allow this, but not the philosophy of animal rights, whose highest principle is justice.”¹³⁷

See The Rights-Based Approach to Animal Ethics for more on this framework.

Utilitarianism

Utilitarianism, a philosophical framework developed by Jeremy Bentham and later expanded by John Stuart Mill, supports the end of animal exploitation by emphasizing the principle of the greatest happiness for the greatest number.¹³⁸

Jeremy Bentham famously applies this principle to animals: “The question is not, can they reason, nor can they talk, but can they suffer?¹³⁹

Peter Singer, a contemporary philosopher, applies utilitarianism to animal ethics in his seminal work Animal Liberation (1975), arguing that causing animals unnecessary suffering for human benefit is ethically unjustifiable. He applies the concept of “equal consideration of interests.”¹⁴⁰

Virtue Ethics

Virtue ethics, first articulated by Aristotle, focuses on the moral agent’s character rather than specific actions or consequences.¹⁴¹

In the context of animal ethics, philosopher Rosalind Hursthouse argues that a virtuous person would be compassionate and kind toward animals—and oppose practices that cause suffering.¹⁴²

The Ethics of Care

The ethics of care, developed by feminist philosophers like Carol Gilligan and Nel Noddings, emphasizes the importance of relationships, empathy, and care in moral decision-making. This approach argues that ethical considerations should be grounded in the nurturing of relationships and the well-being of others, including animals.¹⁴³

From an ethics of care perspective, exploiting animals is wrong because it neglects our responsibility to care for and protect vulnerable beings who depend on us.¹⁴⁴

We have shown that plant-based diets can be healthy and protect against chronic disease and that exploiting animals greatly harms the environment and causes suffering on a massive scale.

If you can live a healthy life without the culpability of paying others to breed, mistreat, and violently kill animals, why wouldn’t you?

By living vegan, you prevent the suffering and slaughter of many innocent lives who would’ve been born or hatched into a system of violence.

An analysis by Animal Charity Evaluators concluded that a person can spare 105 vertebrates a year by going vegan.¹⁴⁵ A popular vegan calculator, using different assumptions, estimates the total number of animals (not just vertebrates) spared annually to be over 300.¹⁴⁶

Many vegans once said, “I could never be vegan.” Our briefing Getting Started with Going Vegan provides helpful suggestions that will send you on your way.