Peter Singer

Based on Wikipedia: Peter Singer

The Spaghetti That Changed Everything

In the early 1970s, a young Australian philosophy student sat down to lunch at Balliol College, Oxford. His classmate Richard Keshen ordered a salad. When asked why he didn't want the spaghetti, Keshen explained that the sauce contained meat—and then he explained why that mattered to him.

Peter Singer had the spaghetti anyway. But within two weeks, he'd become a vegetarian himself.

That lunch conversation would eventually lead to one of the most influential books in modern ethics, reshape how millions of people think about animals, and help launch a global movement that has redirected billions of dollars toward the world's poorest people. Singer's ideas have made him, according to philosopher Helga Kuhse, "almost certainly the best-known and most widely read of all contemporary philosophers." They've also made him one of the most controversial.

From Vienna to Melbourne

Singer was born in Melbourne in 1946, but his family's story begins in darker circumstances. His parents were Austrian Jews who fled Vienna in 1938, after Nazi Germany annexed Austria in what Hitler called the Anschluss—literally, "connection" or "joining." They were among the lucky ones.

Singer's paternal grandparents were not so fortunate. The Nazis transported them to Łódź, a city in occupied Poland that became the site of the second-largest Jewish ghetto after Warsaw. They were never heard from again. His maternal grandfather, David Ernst Oppenheim, was a distinguished educator and psychologist who had collaborated with both Sigmund Freud and Alfred Adler in the heady early days of psychoanalysis in Vienna. He was murdered at Theresienstadt, the concentration camp the Nazis cynically marketed as a "model Jewish settlement" while using it as a waystation to the gas chambers.

Despite this traumatic family history—or perhaps because of it—Singer was raised in a secular household. His father built a successful business importing tea and coffee. The family rarely observed Jewish holidays, and Singer declined to have a Bar Mitzvah, the coming-of-age ceremony traditionally held when a Jewish boy turns thirteen.

Singer describes himself simply as an atheist.

The Education of a Philosopher

Singer's path to philosophy was somewhat accidental. He initially studied law, history, and philosophy at the University of Melbourne. What drew him deeper into philosophy? Conversations with his sister's boyfriend.

Sometimes the most consequential moments in a life are the most casual.

His master's thesis tackled one of philosophy's oldest questions: "Why Should I Be Moral?" It's the kind of question that sounds naive until you actually try to answer it. Why should you do the right thing, especially when doing the wrong thing might benefit you? Philosophers have wrestled with this question since at least Plato's Republic, where a character named Glaucon asks whether anyone would be just if they possessed a ring that made them invisible.

A scholarship took Singer to Oxford, where he studied under R.M. Hare, a philosopher known for developing "universal prescriptivism"—the idea that moral judgments must be universalizable. If you think it's wrong for someone to steal from you, you must also think it would be wrong for you to steal from them in identical circumstances. This demand for consistency would become central to Singer's own thinking.

At Oxford, Singer also encountered J.L.H. Thomas, who taught him how to read Hegel—no small feat, given that the nineteenth-century German philosopher is notorious for his impenetrable prose. In Thomas's classes, students would work through passages of Hegel's Phenomenology of Spirit "sentence by sentence, until they yielded their meaning." Singer later wrote a short introduction to Hegel, proving he'd learned the lesson well.

The Core Idea: Equal Consideration of Interests

To understand Singer's philosophy, you need to understand one deceptively simple principle: the equal consideration of interests.

Here's what it means. Imagine two beings are suffering. One is a human; one is a pig. If their suffering is equivalent—same intensity, same duration—then that suffering matters equally. It doesn't matter who is doing the suffering. Pain is pain.

This is not the same as saying humans and pigs are equal, or that they deserve identical treatment. A pig has no interest in voting or reading philosophy. A human has no interest in rolling in mud (usually). Equal consideration means we weigh comparable interests equally—not that we treat all beings the same.

Singer calls himself a "sentientist." Sentience—the capacity to experience suffering and happiness—is what grants a being moral status. Not intelligence. Not species membership. Not the ability to reason or use language. Just the capacity to feel.

This leads to some conclusions that most people find intuitive and some that most people find outrageous—sometimes in the same breath.

Utilitarianism: The Greatest Good

Singer is a utilitarian, which means he believes the right action is whatever produces the best overall consequences for everyone affected. The "greatest good for the greatest number," as the slogan goes.

But what counts as "good"? Here Singer's thinking evolved significantly over his career.

For most of his life, he was a "preference utilitarian." This view holds that the good consists in satisfying people's preferences—what they actually want, not what someone else thinks they should want. If you prefer chocolate ice cream and I prefer vanilla, neither preference is objectively better. Morality is about helping people get what they prefer.

In 2014, however, Singer announced he'd changed his mind. In a book co-authored with philosopher Katarzyna de Lazari-Radek, he revealed he'd become a "hedonistic utilitarian"—returning to the older view that what matters is pleasure and the absence of pain, full stop. Your preferences matter only insofar as satisfying them makes you happy.

This might seem like an academic distinction, but it has practical implications. A preference utilitarian might respect someone's preference for a dangerous activity, even knowing it will cause them pain. A hedonistic utilitarian would be more inclined to prevent the pain regardless of preferences.

The Drowning Child

In 1972, Singer published an essay called "Famine, Affluence, and Morality" that has been haunting comfortable people in wealthy countries ever since.

The argument goes like this: Imagine you're walking past a shallow pond and see a small child drowning. You could easily wade in and save the child, but doing so would ruin your expensive new shoes. Should you save the child?

Of course you should. Anyone who let a child drown to save their shoes would be a monster.

But now consider: right now, children are dying from preventable diseases and malnutrition around the world. You could save some of them by donating money to effective charities. The cost to you would be roughly equivalent to ruining your shoes—some luxury you'd have to forgo. Is there any morally relevant difference between the drowning child in front of you and the dying child halfway around the world?

Singer argues there isn't. Distance doesn't diminish moral obligation. The fact that you can't see the suffering doesn't make it less real. If you're morally obligated to ruin your shoes for the nearby child, you're equally obligated to sacrifice equivalent luxuries for distant children.

The implications are radical. Most of us spend money on things we don't really need—dining out, entertainment, fashion, gadgets—while people die from lack of clean water or basic medicine. If Singer is right, we're all failing morally, all the time.

Effective Altruism: Doing Good Better

Singer's ideas helped inspire a movement called "effective altruism," which asks not just whether we should help others, but how we can help them most effectively.

The reasoning is straightforward. If you're going to donate money to charity, wouldn't you want to do the most good possible with that money? Some charities are dramatically more effective than others. Distributing anti-malaria bed nets, for instance, can save a life for a few thousand dollars. Other interventions might cost ten or a hundred times as much per life saved.

This leads effective altruists to some counterintuitive conclusions. Maybe you shouldn't volunteer at a local soup kitchen if you could earn more money in that time and donate it to more effective global charities. Maybe you shouldn't donate to your alma mater's building fund when children are dying from easily preventable diseases. Maybe you should take a high-paying job in finance specifically so you can give most of your salary away.

Singer founded an organization called The Life You Can Save, which recommends charities rigorously evaluated for effectiveness by groups like GiveWell. He's also a member of Giving What We Can, an organization whose members pledge to donate at least ten percent of their income to effective charities.

He practices what he preaches. Singer has reportedly given away about a third of his income for decades.

Animal Liberation

Singer's 1975 book Animal Liberation is often credited with launching the modern animal rights movement—though Singer himself prefers to talk about animal "liberation" rather than "rights," since he's skeptical of rights-based moral frameworks.

The book's argument flows directly from the principle of equal consideration of interests. If suffering matters, and animals can suffer, then animal suffering matters. It's arbitrary to care about human suffering while ignoring equivalent animal suffering, just as it would be arbitrary to care about white suffering while ignoring Black suffering, or male suffering while ignoring female suffering.

Singer popularized the term "speciesism"—originally coined by British philosopher Richard Ryder—to describe the prejudice of favoring one's own species simply because it's one's own species. The parallel to racism and sexism is intentional and provocative.

Consider how we draw the line between "humans" and "animals." There are far greater differences between a chimpanzee and an oyster than between a chimpanzee and a human. Chimps share about 98.8 percent of our DNA. They use tools, learn sign language, form complex social bonds, and clearly experience emotions. Yet we lump chimps together with oysters as "animals" while treating humans as categorically different.

What justifies this? Not intelligence—we don't think it's acceptable to experiment on severely cognitively disabled humans. Not language—many animals communicate, and some humans can't. Not social contracts or moral reasoning—babies and people with dementia can't engage in these either, but we don't therefore exclude them from moral consideration.

Singer argues that the only non-arbitrary line is sentience: the capacity to suffer. And that line includes most animals we routinely exploit and kill.

The Hard Cases

Singer's vegetarianism is not absolute, and this surprises people who expect philosophical consistency to mean rigid rules.

He describes himself as "largely vegan but flexible." He doesn't buy animal products for himself but will eat vegetarian rather than vegan when traveling or dining with others. More controversially, he occasionally eats oysters, mussels, and clams—bivalves that lack a central nervous system and almost certainly can't feel pain.

This flexibility reflects Singer's utilitarian framework. The wrongness of eating meat, for Singer, isn't primarily about killing—it's about suffering. An oyster that can't suffer presents no moral problem. Even mammals could theoretically be eaten ethically if they were "given good lives, and then humanely killed, preferably without transporting them to slaughterhouses or disturbing them."

The problem is that virtually no commercial meat meets this standard. Modern factory farming inflicts immense suffering: animals crammed into tiny spaces, unable to move or exercise natural behaviors, subjected to painful procedures without anesthesia, transported long distances in terrifying conditions, and killed in slaughterhouses that prioritize speed over welfare.

Singer has been particularly concerned with fish, whom he calls "the forgotten victims on our plate." A 2010 study he highlighted estimated that humans capture somewhere between one trillion and 2.7 trillion wild fish per year—numbers so large they're difficult to comprehend. Fish nervous systems are different from mammals', and the question of whether and how much they suffer remains scientifically contested. But the sheer scale suggests that even if fish suffer less than mammals, the aggregate suffering could be enormous.

On Animal Experimentation

Unlike groups such as People for the Ethical Treatment of Animals, known as PETA, Singer doesn't categorically oppose all animal experimentation.

This has gotten him in trouble with some animal advocates. In 2006, he appeared on a BBC documentary about animal testing and said that experiments on monkeys for Parkinson's disease research could potentially be justified—if the benefits were significant enough and no alternatives existed.

The logic is pure utilitarianism. If experimenting on a hundred monkeys could lead to a treatment that prevents millions of humans from developing Parkinson's disease, the math might work out in favor of the experiments. The suffering caused would be less than the suffering prevented.

But Singer is quick to note that most animal experimentation doesn't meet this standard. Much of it is for trivial purposes—testing cosmetics, for instance—or produces knowledge of minimal practical value. He also supports the "three R's" that animal welfare advocates promote: Replace animal experiments with alternatives when possible, Reduce the number of animals used, and Refine experiments to minimize suffering.

Singer has defended some actions of the Animal Liberation Front, a decentralized group that has broken into laboratories to document conditions and free animals. He praised activists who in 1984 stole footage from Thomas Gennarelli's laboratory at the University of Pennsylvania, revealing horrific treatment of baboons in head injury experiments. The resulting documentary, titled Unnecessary Fuss after a phrase one researcher used to dismiss concerns, led to the lab's closure.

But he condemns violent tactics like bombings, and he notes that freeing animals from labs is often futile anyway—the animals are easily replaced.

The Point of View of the Universe

One of the perennial challenges for utilitarians is explaining why we should care about maximizing overall welfare rather than just our own welfare. Why adopt "the point of view of the universe"—as the nineteenth-century philosopher Henry Sidgwick memorably put it—rather than looking out for number one?

Singer has wrestled with this question throughout his career. In early work, he acknowledged that pure reason might not compel someone to be moral rather than selfish. You could coherently prefer your own interests to everyone else's, even if doing so was immoral.

But he suggests several reasons why self-interest might actually support morality. There's what he calls "the paradox of hedonism"—the observation that people who directly pursue their own happiness often fail to find it, while people who focus on meaningful projects and relationships tend to be happier as a byproduct. There's also the deep human need to feel connected to something larger than oneself, which a purely selfish life cannot satisfy.

In 2014, Singer went further, arguing that objective moral values actually do exist. In The Point of View of the Universe, co-authored with Katarzyna de Lazari-Radek, he defended Sidgwick's view that some moral truths are self-evident to reason—much as mathematical truths are. We don't need external proof that 2+2=4; we can simply see that it's true. Similarly, perhaps we can simply see that suffering is bad and should be minimized.

This represented a significant shift for Singer, who had previously been skeptical of objective moral claims.

A Career of Consequence

Singer spent most of his career at Monash University in Melbourne, where he founded the Centre for Human Bioethics and twice served as chair of the philosophy department. In 1999, he moved to Princeton University, where he held the position of Ira W. DeCamp Professor of Bioethics until his retirement in 2023.

Along the way, he's engaged with the wider world in ways unusual for academic philosophers. He ran for the Australian Senate as a Greens candidate in 1996 (he lost). He was named Australian Humanist of the Year in 2004. The Sydney Morning Herald listed him among Australia's ten most influential public intellectuals in 2005. He co-founded the open-access Journal of Controversial Ideas in 2018, providing a venue for academics to publish under pseudonyms when their work might invite harassment or career damage.

He also co-founded Animals Australia, one of that country's leading animal advocacy organizations, and has written a regular column for Project Syndicate since 2001, bringing philosophical perspectives to a global audience.

Why He Matters

You don't have to agree with Peter Singer to recognize his importance. He has forced people to think seriously about questions they'd rather avoid: What do we owe to the global poor? What do we owe to animals? Are our moral intuitions reliable guides to ethics, or comfortable prejudices we should overcome?

His influence extends far beyond academia. The effective altruism movement has directed billions of dollars toward evidence-based charities. Vegetarianism and veganism have gone from fringe positions to mainstream options, with Animal Liberation frequently cited as the catalyst. Philosophers who sharply disagree with Singer's conclusions still engage with his arguments—a testament to the clarity and force of his reasoning.

The lunch at Balliol College happened more than fifty years ago. Richard Keshen, the vegetarian friend who started it all, went on to become a philosophy professor at Cape Breton University in Canada. Singer went on to challenge millions of people to reconsider what they eat, what they buy, and what they owe to others.

Sometimes a conversation over spaghetti really does change the world.