A summary of Peter Singer’s Animal liberation. Considered one of the early works that sparked the animal rights movement. It is unfortunate that Singer’s arguments seem subject to various misunderstandings in Korea, such as being paternalistic charity or merely moderate animal welfarism.

On the Korean translation

One of this book’s most important words is “consideration,” appearing frequently in “equal consideration” and “the principle of equal consideration.” Throughout the Korean translation, not just Chapter 1, it is rendered interchangeably as goryeo (consideration) and baeryeo (thoughtful care or kindness). I recommend mentally replacing almost every baeryeo with “consideration.” When paternalistic expressions such as “bestowing benefits on animals” appear, assume they are excessively free translations or arbitrary additions absent from the original.

Editions

There are 6 editions. The first edition came out in 1975, a 40th anniversary edition was released in 2015, and a completely revised edition titled “Animal Liberation Now” was released in 2023.

The 2023 revised edition has changed quite a bit. The main flow and main sentences remain, but many sentences have been changed (generally simplified or deleted), and many new studies and cases have been added. The title of Chapter 4 was also changed; it was originally “Becoming vegetarian,” but in the revised edition, it became “Living without speciesism.” It is a title that encompasses changes not only in diet but also in overall lifestyle.

Yuval Noah Harari’s recommendation in the 2023 revised edition

This is a recommendation written in 2015, and was published under the title “Introduction” in the 2023 revised edition.

It begins by mentioning the negative effects humans have had on the environment from the Stone Age to modern times.

Stone Age:

When humans first settled in Australia 45,000 years ago, 90% of large terrestrial animals became extinct.
When they settled in the Americas 15,000 years ago, 75% of large mammals became extinct.
Archaeological records from other regions show similar patterns repeatedly.
Even before the Neolithic Revolution, humans had already driven 50% of large terrestrial mammals worldwide to extinction.

Next is the Neolithic Revolutionary Period. Domestication starts. More than 90% of today’s large animals are livestock. Animals in the wild also experience pain and tragedy, but after domestication, they begin to experience new types of suffering that are getting worse.

In modern times, as traditional livestock farming becomes industrialized (factory farming), it becomes more cruel. As modern science learned about Virus and began to develop all kinds of technologies, such as Antibiotic, Vaccine, hormones, pesticides, automatic feed dispensers, etc., more animals were crammed into a narrower space and ‘Productivity’ was raised to an extreme level. Today, the total weight of ‘livestock animals’ is approximately 700 million tons. The total weight of humans is about 300 million tons, and the total weight of large wild animals (animals weighing several kg or more) is about less than 100 million tons.

According to these statistics and the book’s claims, factory farming is causing more suffering and tragedy than all wars in human history combined.

Preface to the 2023 revised edition

Although the situation has improved significantly compared to when the first edition of 1975 was published, institutional improvements are said to be limited to a very few states in the United States and European countries.

The preface points out that China’s ‘animal production’ has increased enormously. It is now the world’s largest pig ‘producer’ and also ‘produces’ chickens and ducks in vast numbers, yet has almost no welfare regulations. At the time of writing, China was building a 26-story livestock facility, each floor covering 400,000 square meters. On completion, it would house millions of pigs.

Since the first edition, we have learned much more about animals’ conscious experiences and psychological/physical needs, the effects of greenhouse gases on climate change, and the fact that livestock/dairy emissions are comparable to those of the entire transport sector. The author argues that these findings have strengthened the case for the animal rights movement.

Preface to the first edition

First sentence:

This book is about human tyranny over nonhuman animals. … Most readers will think this is a wildly exaggerated statement. Five years ago, I would have laughed at it too, but I write in complete seriousness. Five years ago, I did not know what I know now.

The author emphasizes that animal rights activism has nothing to do with being an animal lover, just as opposing discrimination against Black people does not require loving Black people.

I do not “love” animals. I simply want them treated as independent sentient beings, rather than as means to human ends (such as consuming a pig’s flesh as sandwich filling).

Singer criticizes humans’ unjust discrimination against nonhuman animals, analogous to sexism and racism. He notes how deeply it is rooted in language: animal ordinarily means “animals other than humans,” revealing our speciesist prejudice. Humans and chimpanzees are biologically far closer than chimpanzees and oysters, yet we lump chimpanzees and oysters together as “animals” while separating humans.

The recent Korean shift from “pet” to “companion animal” is similar: replacing a term suggesting a living toy that gives us pleasure with one conveying an animal we live alongside.

Last sentence:

If we stopped raising and killing animals to eat, we could produce much more food for humans, and if distributed properly, could possibly eliminate hunger and malnutrition throughout Earth. Animal liberation is also human liberation.

Chapter 1. All Animals Are Equal

Chapter 1 explains why animal liberation is necessary. Rather than approaching it as “let us humans bestow benefits on poor animals,” Singer seeks to give logical grounds for why humans’ current treatment of animals is unjust and discriminatory.

The basis of equality

The first step is defining equality. For the author, equality means ‘equal consideration,’ rather than ‘equal treatment.’

The implications of the principle of equality are not a description of substantive equality between humans, but a prescription for how we should treat humans.

For example, because men are biologically unable to become pregnant, Abortion rights is a right that can only be guaranteed to women. Even if women have the right to terminate pregnancy and men do not, it is not discrimination. There are two important things in this example. First, we should not claim that men and women are equal because they are biologically the same. Regardless of whether there is a difference, we must say that we are equal. Second, equality is not ‘equal treatment’ but ‘equal consideration’.

The racism problem can be viewed from the same perspective. Some people argue that whites and blacks are equal because there is no fundamental difference between them except their skin color. But Singer says there is a problem with this approach. We should say that groups are morally equal, not because there are no differences between them, but even if there are large and fundamental differences.

Likewise, non-human animals and humans do not have to be exactly the same to demand equal rights. Equal rights do not mean equal treatment (e.g., guaranteeing voting rights to non-human animals). This is called the principle of equal consideration.

Bentham’s question

Some accept the principle of equal consideration but restrict its scope to humans. Jeremy Bentham argued for expanding it. Distinguishing humans as deserving moral consideration because they can speak or reason, while excluding nonhuman animals, is arbitrary. We need a nonarbitrary criterion for moral consideration. Bentham proposes “Can they suffer?”

The ability to experience pleasure or pain is sentience, and those possessing it are sentient beings. Sentience means an individual has interests. Those interests deserve equal consideration, whatever they are and whatever species the individual belongs to. Excluding an interested being merely because they are not human, or assigning human interests greater importance than nonhuman animals’ without reason, cannot be morally justified. This is speciesism.

(An explanation of the concept of ‘rights’ follows; refer to Utilitarian’s view on rights.)

Who can suffer?

How do we know if non-human animals feel pain? The author asks, “How can I know if other humans besides me feel pain?” Because pain is an individual’s conscious experience, humans have no way to objectively know about the pain of others. This is called Problem of other minds. Nevertheless, humans are convinced that other humans will feel pain as a result of only observing their external states (facial expressions, actions, speech, etc.).

If other animals resemble humans neurologically, physiologically, anatomically, pharmacologically, and cognitively, it is reasonable to suppose they can probably suffer. According to the 2012 Cambridge Declaration on Consciousness, humans and nonhuman animals share many similarities, and a considerable range of animals (including insects, which are invertebrates) are very likely to experience pain.

Drawing the line

There is no academic disagreement that at least some nonhuman animals have conscious experiences. Debate concerns which particular species do. How far should the principle of equal consideration extend?

It is relatively clear that mammals, birds, reptiles, and amphibians have conscious experiences. Fish are another group of vertebrates we kill in particularly large numbers. Victoria Braithwaite, author of Do fish feel pain|Do fish feel pain?, notes that fish have nociceptors, display characteristic pain behavior when physically hurt, and return to their original behavior when injected with painkillers. Some fish also show well-developed cognitive abilities, such as cooperating to hunt.

Similar research continues to emerge for various invertebrates (insects, octopuses, etc.).

Implications

So far, we have seen that 1) many animals can suffer, and 2) no argument justifies giving their suffering less consideration than human suffering. What are the practical implications?

Under the principle of equal consideration, individuals differ and so do their interests; interests of similar magnitude should receive similar consideration. But interests vary greatly by species and by the circumstances of individuals within a species, making it difficult to determine precisely how much consideration of which interests amounts to ‘equal’ consideration.

However, from a practical perspective, precision is not important. This is because the pain that humans are currently inflicting on non-human animals is enormous, but humans’ consideration for them is so minimal that it is clear that it is a problem even without looking at it closely.

When is killing wrong?

Applying the principle of equal consideration to suffering is relatively easy, at least theoretically, but defining wrongful killing is more complicated. This book will not focus on killing, because suffering alone already gives us ample reason to stop factory farming.

Reference: Peter Singer’s view on killing

Chapter 2. Tools for Research

In the US, the USDA counts experimental animals, but includes only certain animals such as monkeys, dogs, and rabbits, excluding rats, mice, and birds. Its figures indicate about 800,000 animals are ‘used’ annually. Extrapolating to all experimental animals gives an estimated 15–110 million used annually in the US alone as of 2018.

Making monkey psychopaths

ToDo

Psychology’s ethical dilemma

ToDo

Learned helplessness

ToDo

Poisoning, blinding, and other ways of testing on animals

ToDo

Medical experiments

ToDo

Conditioned ethical blindness

ToDo

Not even good science

ToDo

Ineffective regulation

ToDo

When are experiments on animals justifiable?

ToDo

A way forward?

ToDo

Chapter 2 presents examples of abuse of experimental animals and discusses why animal testing is problematic, why it persists, and how it should change.

Chapters 2 and 3 demonstrate the enormous suffering inflicted on animals through human speciesism. I suspect they also aim to shock readers by revealing human cruelty, prompting a resolve to change. Chapter 2 is so gruesome that I will record only minimal experimental details.

Military experiments mainly use monkeys, sometimes chimpanzees, training them through repeated electric shocks to perform desired behaviors. After several weeks, the experiments proper begin: measuring, for example, how well they maintain trained behaviors before dying after exposure to radiation or toxic chemicals. Monkeys and chimpanzees are used because they are evolutionarily close to humans. In phylogenetic terms, proximity runs in this order: monkeys–gorillas–chimpanzees–bonobos–humans.

Civilian experiments are just as cruel. These are experiments I saw in psychology textbooks (social psychology, developmental psychology, evolutionary psychology) and often encounter in popular science books. The details are too cruel to recount. What shocked me was that the textbooks had not included a single line explaining how brutal these procedures were.

The following discussion criticizes the vast scale of animal experiments, the absence of regulation for most research, researchers’ treatment of experimental animals as tools rather than living beings, and the perpetuation of these research traditions.

Singer also criticizes how most studies kill animals without meaningful conclusions, and how even their findings can be exceedingly trivial. As a utilitarian, he seems to be saying that if suffering has already been inflicted, substantial findings should at least result; instead, enormous suffering is inflicted for no reason or for trivial ones.

Singer does not, however, categorically oppose every kind of animal experiment. To assess whether an experiment is justified, he recommends asking yourself:

If a child is 6 months old, an orphan, and has suffered severe brain damage that makes normal neurological development impossible, is it justified to use this child in animal testing?

Singer’s criterion is that only if you can answer “yes” is the experiment justified, at least by your own internal standards. Six months is specified because the child would be no more cognitively advanced than other large primates; being orphaned excludes family members’ suffering from consideration (whereas most experimental animals are forcibly separated from mothers, causing the mothers severe suffering too); incurable severe brain damage reduces consideration of the child’s future potential.

Singer argues that if you answer, “You shouldn’t use this child, but it’s okay to use animals,” that’s speciesism (special treatment of the human species).

There will be some gray areas within this standard, but Singer says we don’t have to worry too much about these gray areas. Because most of the abuses that humans are committing today are so vividly black that they don’t even come close to the gray area, and if we could just reduce these abuses, the world would improve greatly. In other words, Singer does not oppose all animal testing in principle, but considering the experiments currently taking place in reality, Singer’s position is that in reality, all experiments should be stopped immediately.

The last paragraph of Chapter 2 ends like this:

Because abuse of laboratory animals is only part of the larger problem of speciesism, it will be difficult for the problem of abuse of laboratory animals to disappear unless speciesism itself disappears. No doubt, someday in the future, our children’s children will read about what happened in 20th century laboratories and feel the same shock we felt when we read about Roman gladiatorial arenas or 18th century slave trade.

I think that Singer’s way of thinking (judging what unfair discrimination is based on utilitarianism) can comprehensively explain at least one aspect of various types of discrimination (racism, Sexism, Ageism, speciesism, etc.). So, I thought that historically, these social movements could have united with each other (animals + environment + women = Ecofeminism, race + women = Black feminism, class + feminism = Marxist feminism, etc.).

Chapter 3. Down on the Factory Farm

Chapter 3 describes chickens, pigs, calves, dairy cows, and cattle (raised for beef) in factory farming, then abuses common across livestock: transport and slaughter, dehorning, castration, branding, and so on. Although less gruesome than Chapter 2, these examples are also very cruel, so I will recount them only briefly.

Chickens can do little but sleep, lay eggs, and eat in spaces too cramped for movement. Stress makes them aggressive, pecking other chickens; because this reduces factory productivity, parts of their beaks are removed. Beaks contain sensitive nerve tissue comparable to the area between human fingernails and flesh, causing lifelong pain. Floors are simply perforated metal bars to facilitate waste removal, and many chickens’ feet become entangled with the bars. The examples grow increasingly cruel through pigs, dairy cows, cattle, and calves, but I will omit them.

Pigs and cattle experience additional suffering during transportation and slaughter.

Some people must only eat meat from animals slaughtered while conscious for religious reasons (Judaism and Islam), so there are cases where slaughter is performed without stunning or anesthetizing the animals. Likewise, because there are quite a few parts of meat slaughtered this way for religious reasons that should not be eaten, these parts are said to be sold as general products regardless of the religion in question (because it would be a loss to throw them away).

Several European countries, including Sweden, are reportedly trying to reduce livestock abuse. Legislation progresses very slowly in the United States because lobbying groups are so powerful. Korea is not specifically discussed, but the book says “other countries are at similar or worse levels than the US.” See Slaughter statistics for the situation in the Republic of Korea.

Although Singer spends a lot of time explaining the treatment of animals, he does not take a compromise position of only improving welfare while maintaining factory farming. Singer says “humane animal husbandry” is just a better form of speciesism:

(Humane animal husbandry) is only an enlightened and more humane form, but it remains the same as speciesism. No government has yet questioned the notion that animal interests are less important than human interests. The issue is always about ‘avoidable’ suffering, which is limited to avoidable suffering provided that the same amount of animal products are produced and costs are not significantly increased. The assumptions that humans can use animals as means for their own ends and that animals can be raised and killed to satisfy various human preferences, including animal flesh, have never been challenged.

As an aside, I found two familiar names in the discussion of chickens and noted them down.

First, Konrad Lorenz, a founder of ethology and Nobel Prize winner, especially known for research on imprinting in birds. He was also something of a teacher to Richard Dawkins, famous for The selfish gene (Dawkins’s direct teacher was Niko Tinbergen, Lorenz’s colleague). It is unfortunate, though, that Lorenz collaborated with the Nazis.

The other is Marian Dawkins, a scholar and Richard Dawkins’s former spouse. Like him, she studied ethology at Oxford. Later, alongside research on animal consciousness, she was also involved in animal welfare activism.

Chapter 4. Becoming a Vegetarian

Chapter 4 proposes Vegetarianism as a social movement and personal practice method to combat speciesism, which is prevalent in human society. It is argued that vegetarianism can not only reduce speciesism, but also solve food shortages and contribute positively to environmental problems. It also contains practical content, explaining how to gradually become a vegetarian, what you can and cannot eat, why you can and why you cannot, etc.

First, here is an explanation of why vegetarianism is an effective social movement.

It is important to encourage politicians to carry out various legislative activities to protect animal rights, but it is difficult to do this alone. This is because the industry that profits from exploiting animals has developed greatly and is engaged in various lobbying activities. Some large animal rights groups tend to focus too much on the welfare of popular companion animals (Dog, Cat) or animals that we generally do not eat (Polar bear, monkey, etc.). Considering this, it is argued that the most powerful attack is to reduce financial motivation, that is, to reduce meat consumption.

Second, unlike other symbolic movements, even if vegetarianism fails on the macro scale, at least the animals I did not eat have been spared that suffering.

The next topic is a rebuttal to the question that if factory farming is eliminated, the efficiency of food production will decrease and the food shortage for humanity will become more serious. According to Singer, compared to eating the plants directly by humans, going one step further, such as feeding the plants to cows and then eating the cows, causes extremely low efficiency, uses more water in the process, destroys more rainforests to grow feed crops, and makes water more polluted by waste (mainly excrement) from factory farming. Specifically, they say that if Americans reduced their meat consumption by just 10%, they could produce more food to feed 60 million people.

(For more detailed and recent calculations, see Efficiency of plant-based diet)

Next is nutrition: the concern that, since humans are classified as omnivores, a vegetarian diet might create nutritional problems. Historical vegetarians including Gandhi, Leonardo da Vinci, Leo Tolstoy, and George Bernard Shaw reportedly lived long, healthy lives. The book explains that the only nutrient difficult to obtain from plants is vitamin B12, which can be obtained from some fermented foods, or, if that is difficult, from supplements.

Singer says vegetarianism actually offers several health advantages over eating meat, but he deliberately keeps the nutritional case minimal—roughly “vegetarianism is no worse”—rather than explaining those benefits at length. He worries that dwelling on them could make his argument seem aimed at human rather than animal interests. (On vegetarianism, especially whole-food plant-based diets and health, see The China Study.)

Finally, what should and shouldn’t we eat, and why? The basic principle is Chapter 1’s “principle of equal consideration for all sentient beings.” If a being can experience pain or pleasure, its interests (reducing pain and increasing pleasure) deserve equal consideration. On this basis and biological knowledge, the author’s fuzzy line lies “somewhere between shrimp and oysters.” That was in the first edition (1975); the revised edition (2009) changes this: we cannot be completely certain oysters feel no pain, and avoiding them is relatively easy, so it is better not to eat them where possible. What matters, he says, is each person determining the scope of their practice from the principle, rather than precisely following his proposed boundary.

Examples of the author’s guidelines: avoid meat such as beef, chicken, and pork, and all fish; eat eggs only from free-range farms, otherwise avoid them; do not drink milk; avoid dairy products where possible, but eat them if avoiding them is difficult (milk appears in so many products that complete avoidance is practically difficult). Adopt these steps gradually according to your circumstances. (Dairy alternatives are now far more varied than they were then.)

Singer is most wary of situations in which changes in reality cannot be made because of the pursuit of moral perfection. The purpose of the animal liberation movement he thinks is not to completely isolate those who participate in this movement from all evil deeds and make them morally perfect human beings. In other words, it is not important to make individual participants think, ‘Oh, I am a good person.’ The purpose of the animal liberation movement is to realistically reduce the unfair oppression of non-human animals and the suffering they experience.

Chapter 5. Man’s Dominion

Chapter 5 defines that almost all humans around the world are speciesists and traces why speciesism has become so widespread. While reading Chapter 5, I felt that the author was very critical of Christianity, but when I looked it up, I found that he was indeed an atheist, and that he was not just an atheist, but an active atheist. I hope you read it with that in mind.

Singer’s goal is to encourage an animal liberation front that fights against speciesism, and he uses two major strategies in this book. Chapters 2 and 3 are a frontal attack (denouncing the cruelty of speciesism currently practiced), and chapter 5 is a back attack (revealing how weak the ideological/historical foundation of speciesism is). For this purpose, the author critically describes the history of speciesism.

Singer divides speciesism’s history into three stages: pre-Christianity, the Christian era, and the Enlightenment and after. The usual Eurocentric sequence is Archaic Greece, Classical Greece, Rome, the Middle Ages, the Renaissance, the early modern period, and the contemporary period. Roughly connecting the two, “pre-Christianity” corresponds to Archaic/Classical Greece, the Christian era to Rome/the Middle Ages, and the Enlightenment and after to the Renaissance/early modern/contemporary periods.

pre-christianity

From the perspective of speciesism, it is said that the attitudes of Westerners toward animals during the pre-Christian period were influenced by two ideologies.

One is the Jewish tradition, the other the ancient Greek tradition. The Jewish creation story (the Christian Old Testament’s Genesis) says animals were created as means for humans, that human males were corrupted by animals and women, that fallen humans became ashamed and wore “animal skins,” that exiled humans’ descendants offered animals as sacrifices to God, and that God killed animals through floods and fire and brimstone. The author regards Jewish scripture as profoundly speciesist.

The other is ancient Greek thought, also divided in two from the perspective of speciesism: the Pythagorean tradition and the line from Socrates through Plato to Aristotle. The Pythagoreans were strongly religious (mathematics has a mystical aspect, so mathematics and religion have surprising affinities), and especially kind to animals because they believed dead humans’ souls entered them. The Aristotelian tradition regarded animals as different from humans. Unfortunately, the Platonic-Aristotelian tradition became mainstream Western philosophy.

Christianity

The author sees what we call Christian culture as the combination of the Roman Empire’s militaristic culture (the weak, slaves, captives, and animals were worthless) with Jewish and Aristotelian traditions. Rome originally treated fights to the death between humans, between humans and animals, and between animals as sport. But under Jewish and Aristotelian influence, human-versus-human sports (as depicted in Gladiator) disappeared by the fourth century.

Christian philosophy developed greatly in the Middle Ages, with Thomas Aquinas particularly influential regarding animal rights. His ethical system classified sins as against God, oneself, or other people, leaving no place for animal abuse unless humans were involved. This influence lasted remarkably long: a Vatican statement in the mid-nineteenth century opposed animal rights legislation on this basis. (The Vatican’s position began to change only under John Paul II in 1988.)

Enlightenment and After

After the Middle Ages, Renaissance humanism shifted thought from God to humans. But humanism was literally about “humans,” not animals, so animal rights improved little. A few figures nevertheless stand out, the most famous in the book being Leonardo da Vinci, who became vegetarian for animal rights reasons.

From an animal rights perspective, the thinker who had the most negative influence during this period is René Descartes. Because Descartes was both a mechanist and a Christian, he had no choice but to advocate dualism (matter and soul) in order to integrate mechanism and Christianity, and said that all things in the world are machines, but humans are the only ones with a soul given by God. In other words, animals are just somewhat complicated clocks. Without a soul, there is no consciousness, and without consciousness, you cannot feel pain, so you can experiment as you like. From this period, animal experiments began to bloom.

These experiments were cruel (nailing live dogs’ limbs down and dissecting them alive—though even this is mild compared with Chapters 2 and 3), but also prompted doubts: “Are animals really machines? It doesn’t seem so.”

1859 has On the origin of species published by Charles Darwin. And about 10 years later, Darwin published The descent of man, and selection in relation to sex, and a little later, The expression of the emotions in man and animals. Combining the messages of these three books, it can be summarized that all modern species started from one or a few species and gradually differentiated through the process of evolution by Natural selection (the origin of species), humans are also the same (the origin of humans), and there are many similarities between humans and large primates (about the emotional expression of humans and animals). This ideological change is usually called Darwinian revolution.

By the twentieth century, much of the public understood, at least rationally, that humans and animals differ in no fundamental way, yet remained in an uneasy state, unable to eradicate longstanding speciesist habits of using animals as means. The author sees this as continuing today: the “age of excuses.”

Chapter 6. Speciesism Today

Chapter 6 introduces resistance to the animal rights movement, the logic of opposition to animal rights, and the author’s counterargument.

The chapter begins with culture and education, criticizing adults for instilling two opposing views of animals long before children can think independently: cute storybook creatures, or meat we eat. Just as feminists criticize stories and films reinforcing female gender roles and propose stories depicting diverse femininities, animal advocates should help children learn that animals are sentient beings equal to humans.

The media also fail to show the realities of factory farming or animal experiments. Speciesists’ first defense is therefore ‘ignorance’: claiming not to know, or refusing to listen to explanations and striving to remain ignorant.

Another problem is the attitude of “people come first.” This attitude is itself speciesist. Moreover, human oppression of animals generally results from the attitude of humans viewing animals as means, rather than from a fundamental conflict of interest between animals and humans. For example, becoming a vegetarian is not as difficult as you think. If enough people adopted a vegetarian diet, we could effectively reduce factory farming, one of the greatest oppressions on animals.

The false prejudice of noble humans versus cruel beasts is also one of the driving forces that maintain speciesism. However, when war is taken into consideration, humans are one of the most cruel species. Humans tend to underestimate the brutality of humans and overestimate the violence of animals, but this is also just speciesism.

Some argue that humans eating animals is part of the natural order of things. However, citing nature as a basis for explaining justification is not a wise strategy. If we follow everything that is natural, it will be a tragic world. For example, war can be said to be natural for humans in that there has almost never been a time in human history without war. But we don’t all have to run to the battlefield to lead a natural life. (Although it is not specified in the text, this type of error is called Naturalistic fallacy. If a proposition about value is derived solely based on propositions about fact, a naturalistic error is committed.)

Some argue that because humans eat cows, the cow population has increased to what it is now, so meat-eating is beneficial to cows. The argument is that it is a good thing that cows were born that would not have been born if humans had not eaten meat. I would like to introduce one of Singer’s many counterarguments to this claim because it is interesting.

If, as this person claims, the creation of more life is a good thing, it would be better to have more humans than cows. Because this person is a person who advocates meat-eating, it is clear that he considers humans to be more important than cows. Food is needed for more people to be born, and the best way to secure more food is to become vegetarian. This is because humans eating plants directly is much more efficient than feeding plants to cows and then eating the cows. Therefore, people who make these claims should immediately stop eating meat and become vegetarian in order to carry out their claims as much as possible.

Lastly, Singer once again emphasizes that while writing this book, he tried to develop logic by appealing to reason as much as possible.

I have appealed to reason rather than emotion or sentiment. Not because I fail to understand the importance of kindness or feeling toward other animals, but because I believe reason is more universal and compelling.

The author’s attitude remains consistent in his most recent book, The most good you can do. Singer believes that we can change the world for the better through the power of reason.