Peter Singer's Argument for Animal Liberation in All Animals Are Equal

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Table of Contents

  • Introduction 
  • Authors That Influenced His Work
  • Principle of Equal Consideration of Interests
  • Speciesism
  • Singer's Critics
  • Blindspots


By rephrasing the essay question, this essay will be assessing Peter Singer´s argument for animal liberation by describing and evaluating his two main ideas: principle of equal consideration and speciesism. Firstly, this essay will investigate the opinions of his predecessors that were fighting for animal rights to understand his background. Secondly, this essay will discuss essential arguments raised by Peter Singer. Thirdly, this essay will show two Singers critics, Cohen and Kaufman and discuss their arguments. By looking at the criticism, we will evaluate arguments against from other thinkers. Lastly, this essay will show points that Singer left unanswered in his work.

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Authors That Influenced His Work

In order to better understand Peter Singer´s argument for animal liberation we will investigate the background and thinkers that were fighting for animals’ rights before him in order to better understand where his arguments originate.

It was Darwin´s theory of evolution released in the second half of the 19th century that changed thinking of the society in the current time. His revolutionary idea was that humans come evolutionary from animals and not from God, which pointed out human similarity to animals. This finding is what helped to better understand the nature and humans as the part of the nature. 41 Nevertheless, that was not enough to convince people to get rid of their dominant position and start to think of animals as their equals. Another very important figure was Jeremy Bentham who was defending animals’ rights. Peter Singer mention Jeremy Bentham in his work often and therefore we will mention him here. Page 8, anglicka kniha na talisu. Bentham´s main argument was that animals should be involved in our moral thinking. He was focusing on the Principle of equal consideration of interests. Condition for being to have moral status is the ability to suffer. Uniquely he attached animals to this theory as well. He argued that because of the ability to suffer, we should rethink the way we treat living being around us. 43 His quote is each counts for one, none for more than one….. 

Last very important author that influenced Peter Singer was Henry Salt. In his book, Animals Rights from 1892 he focused on the difference in the way people treat other people and how they treat animals. His main thought was that animals should have moral rights if people have them. Main criteria for this was that because a being realize themselves, they should have rights. And as there was an evidence that animals can do it, there is no reason why we should deprive their rights. There are two essential points for Singer´s argument for animal liberation, those are principle of equal consideration of interest and speciesism. This essay will now describe each of them in detail.

Principle of Equal Consideration of Interests

In his book Animal Liberation (49) Peter Singer proposes the argument for animals as rightful owners of the principle of equal consideration of interests. He begins by comparing animals to the position of women or different races in the past. Women were raised to listen to their dad and after they were wed, to listen to their husband. They were not allowed to vote or make big decisions by themselves. 

After the principle of equality was brought upon them as well, women gained same rights like men. Nevertheless, that does not mean that men and women should have same rights. They are different and because of that they cannot have the same rights. Examples mentioned in the book are abortion and voting. Why would men need to have women´s right to abortion or why would dogs need to have human´s right to vote, if neither of them actually needs this right. 

Therefore, the principle of equal consideration of interests requires identical approach but different understanding. Singer requires to look at individuals and their capabilities instead of judging them as a whole group. He requires individualism to avoid sexism or racism. Like the argument that men are more competent to work than women. 

Singer argues that it is not morally right to benefit one group just because it has always been like that. Nowadays, people are not equal because they always saw themselves to be equal. They had to change things and fight for equality to create it among those who did not agree with it.65 Just like with animals, which is why they are entitled to the principle of equal consideration of interests. He supports this argument by saying that if we compare animals to humans according to basic human characteristics, it will be evident that they barely differ. Animals are able of self-realization, as Lesley Rogers demonstrated. He proved that animals are able to realize their reflection in the mirror and that also they are able to realize the difference between past and the present. 

In the question if animals should have rights, Descartes found that language is very important sign. It has been proved that animals are able to learn sign language, that they communicate within each other and that if they are provided with voice transformer, they are able to speak. Therefore, if the equality comes from the personality trait there would have to be a set threshold in order to assess this theory. That has a setback, if there was a limit set low enough that it would cover all humans, such as babies, disabled and retarder humans, the threshold would cover some animals as well and wise versa. 

However, the limit of abilities of some people does not take away their rights. Singer says that the differences in the abilities of humans does not justify any difference in considering their interests. We should give the same weight to our interests just like to the interests of anyone else, because an interest is an interest. In order to the equal consideration of interest to be really equal, it should not be dependent on human abilities or their gender or race according to Singer. It should be based for everyone so that it is equal. Person is not less valuable because he/she is less intelligent than others. This thought originates from Jeremy Bentham and Singer developed it. 

Ability to suffer should be the basic condition to in order to say that being has an interest. Singer developed this theory by including the ability to feel happiness and enjoyment as well. Because of the ability to feel happiness, it is in the interest of the being to feel more happiness than sadness. Singer as an utilitarianist was keen to maximize happiness and minimize sadness. Animals are able to feel pain and happiness, thus that makes them moral figure and gives them moral status. Since animals can suffer, we must take into account their suffering like suffering of any other living being. It does not matter if it human being or animal.


According to the British Oxford dictionary, speciesism is defined as favoring humans over any other species, which is based on human superiority. Singer agreed that sometimes, humans can suffer more than animals because they can connect situations with pain and therefore be scared even before the situation happens. Therefore, sometimes we should prioritize people over animals, nevertheless that should be happening only exceptionally. Term speciesism was brought up first by psychologist Richard Rogers but was popularized by Peter Singer. Singer compares this type of discrimination to racism and sexism, the reason is that speciesism violates the principle of equal consideration of interests just like racism did. It is done by using the moral differences between humans to rationalize the justification of the difference in the treatment between different groups.99 Just like spiciest give bigger weight to the interest of the members of their own specie when there is a contradiction between their interests and interests of other group of species. Concluding this point it would mean that nowadays, the whole society is species because it is ordinary that animals are used for the purposes of people. Later in the Animal Liberation book, Singer focuses on two illustrations of speciesism – experimentation on animals and killing animals for food. These two are heart of the issue with speciesism. They cause more harm than anything humans do.

Therefore, if a being suffers, there can be no moral justification for it no matter what the nature of the being is. The principle of equality requires that anyone who is suffering should be accounted equally. If a being is not capable of suffering or to experience enjoyment of happiness, there is nothing to be taken into account. 

Singer's Critics

One of the biggest Singer's critique was Cohen. He argued that the ability to have rights and understand law is the requirement for one side to be able to use it against the other one and that can work only between beings that can understand law. From this reason, rights are only for humans and their owners can be only humans. Since only humans are able to determine moral laws for them and for others, animals cannot. He continued by arguing that compared to people, animals do not have the ability to create moral assumptions, therefore they cannot apply their moral interests or demands and from that reason they cannot have any rights. Moreover, he points out that any similarity between human and animal abilities is irrelevant. 

Cohen also attacks Singer´s argument about taking away moral status because of the deficit in the person abilities. He uses the same argument that it is irrelevant to compare people´s to animal's abilities. He says that Singer is wrong by saying this and that even though people are disabled, the abilities they preserve are incomparable. Cohen believes that all people, including babies, old people, mentally ill people or disabled people, belong to the same moral community which is not allowed for animals. He argues that people do not hold moral right because of their abilities but because of their moral status. The evidence he proposes is that rights are universally human, they grow in human moral sphere. 

Another Singer´s critique was Frederik Kaufman. Kaufman agrees with Singer in the argument that if you can hurt or merit only those entities that have interests, the essential condition is to have interest. Nevertheless, he disagrees in the understanding of the term interest. He says that if we understand interest as something that someone lusts for, it is in the moral interest relevant only to the beings that have psychological abilities because only these beings can have desires. Alternatively, if the mentality is not necessary in order to have interest, then we would have to take into account much more beings. 226 He says that if the mentality would not be necessary, then we would have to consider plants and ecosystems. Kaufman develops the argument even more by saying that machines would have interests as well… 227 He also points out difference between preference and interests. He says they should not be combined.

He also points out, that in order to have interest, person does not need to have preference contrarily to Singers opinion. According to Kaufman interest and preference are different concepts. He says that in order to have preferences, living being needs to have certain characteristics like memory and belief. In other words, for a living being to prefer one thing over another one means that they need to be able to contrast these things and be intellectually sophisticated.228 From this reason, this principle cannot be applied to all sentient living beings because not all of them have the abilities to have preferences.


As much as Singer´s argument for animal liberation is strong. There are few topics that have not been explained. We are missing an answer to the question of what about overpopulation of animals. If we abolished farms like Peter Singer wishes, what would happen with all the animals. There would not be anyone that would be able to take care of them because there would be missing money for it. Another question that comes up is what about the argument that farm animals own their life to the farmer that fed it and raised it? Lastly, what about the question that all humans are natural carnivores?

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