Home / A. Sentience and moral status / Part DIR
"Animals aren't persons."
"person" is a concept we created, and that we already apply to companies, ships and rivers. Using it to decide who may be killed is choosing the definition that produces the desired conclusion. By the classic criterion of personhood, Locke's, human babies aren't persons either, and some animals come closer to the criterion than they do.
Short answer
This argument settles the question by the choice of word. If "person" means self-awareness and plans for the future, then newborn babies aren't persons either, and elephants, great apes and dolphins come closer to the criterion than they do. If "person" means a legal holder of rights, remember that companies are legal persons and that the Whanganui River, in New Zealand, was granted legal personhood in 2017. Personhood is a tool we grant, not a fact of nature.
For children
Words are invented by us. "Person" is one of them. Did you know that, in the law, a company is also a "person"? It has no body and feels nothing, and still it can have rights on paper. So calling someone a person isn't what decides whether they can feel pain. What decides it is having a body and a mind that feel. A pig has those.
"Does a company feel pain? Then why is it a person and the pig isn't?"
Como pode aparecer
"Animals are things, not people."
"Are you comparing a pig to a person?"
"It isn't a subject of anything; it's property."
"Vegans think cows are citizens."
"So will the chicken get a passport?"
"A person is a self-aware being, able to recognize itself over time and take on responsibilities."
"Legal personhood presupposes the capacity to bear duties."
"Everything in its place: people are people, animals are animals."
The strongest version
"Animals aren't people. People are people, animals are animals."
Strongest version (steelman):
- P1Only persons have full moral status and can hold rights.
- P2A person is a self-aware being, able to recognize itself as the same over time, to make plans and take on responsibilities.
- P3Animals aren't persons in this sense.
- CSo animals don't have full moral status and may be used.
P2's definition comes from John Locke, who described a person as a thinking, intelligent being, with reason and reflection, able to consider itself as the same thinking thing in different times and places. It's a psychological definition, not a biological one: it doesn't say "member of the human species".
There's also the legal version, used in courts: a person is whoever can hold rights and duties. This was the criterion adopted by the majority of the New York Court of Appeals in the case of Happy the elephant, in 2022.
The argument is valid. Its soundness fails because P2 and P3 can't both be true without excluding human babies, and because P1 makes a definition we chose into the source of moral value.
Full answer
- a
Reconstruction and diagnosis
The word "person" is used in at least three senses, and the argument switches between them as convenient.
Sense What it means Who's included Biological A member of the species Homo sapiens All humans, no animals. But then "person" is just another name for species, and the argument becomes A10 Psychological (Locke) A self-aware being that recognizes itself over time and makes plans Typical adult humans and, probably, great apes, elephants, crows and dolphins. A newborn is left out Legal An entity to which the law assigns rights and duties Humans, companies, ships, foundations and, in some countries, rivers and animals This is the book's clearest case of the definist fallacy: the definition that produces the desired answer is chosen, and then the answer is presented as a discovery. None of the three senses does the work the argument needs.
- b
Where the argument breaks
1. In the psychological sense, it proves too much.
By Locke's criterion, a three-month-old baby isn't a person: they don't recognize themselves as the same being over time or make plans. Whoever holds P2 must accept that killing a baby wouldn't harm a person, or abandon the criterion.
2. In the psychological sense, it includes animals.
Elephants recognize their own image in a mirror (Plotnik, de Waal and Reiss, 2006). Scrub jays (Aphelocoma) remember what they hid, where and how long ago, adjusting their behavior to the type of food, which has been called episodic-like memory (Clayton and Dickinson, 1998). If that's the criterion, it doesn't divide species the way the argument wants.
3. In the legal sense, personhood is a tool, not a fact.
Companies are legal persons and feel nothing. In 2017, New Zealand recognized the Whanganui River as a legal person, with legal representatives, through the Te Awa Tupua Act. In 2022, Ecuador's Constitutional Court recognized individual animals as subjects of rights (see A7). The law grants personhood when it decides to protect something; the question is whether there's reason to protect, not whether the label has already been granted.
4. The Happy case shows the argument in action, and its fragility.
In 2022, the New York Court of Appeals denied, by 5 votes to 2, the habeas corpus sought for Happy the elephant, holding that the writ applies only to human beings and that a person is someone who can bear duties and social responsibilities. In dissent, Judge Rivera observed that humans without full rights have been able to use habeas corpus, and that the majority failed to explain why an autonomous being of another species couldn't; Judge Wilson recalled that the writ was historically extended to enslaved people, who also had no recognized duties.
5. The moral question doesn't depend on the word.
Even if we agree to call only humans persons, there's still a being who feels pain, fear and pleasure. Sentientism doesn't need the concept of person: it only needs someone for whom things can go well or badly.
- c
Data and sources
Finding or decision Source Note An Asian elephant recognized her own image in a mirror and touched a mark visible only in the reflection Plotnik, de Waal and Reiss, 2006, *PNAS* One of the individuals tested passed the mark test, a common result in this kind of experiment Scrub jays remember what they hid, where and how long ago, and retrieve perishable food first Clayton and Dickinson, 1998, *Nature* Called episodic-like memory; its interpretation as "mental time travel" is still debated The New York Court of Appeals denied habeas corpus for Happy the elephant by 5 votes to 2; a person is whoever can bear duties and responsibilities Nonhuman Rights Project v. Breheny* (2022), analysis in the *Harvard Law Review The dissents by Rivera and Wilson are central to this chapter The Whanganui River recognized as a legal person, with legal representatives Te Awa Tupua Act, New Zealand, 2017 Shows that legal personhood requires neither sentience nor duties Individual animals recognized as subjects of rights Constitutional Court of Ecuador, Estrellita case (2022), dealt with in A7 None of these decisions required animals to take on duties - d
The strongest counter-reply: person as a moral concept, not a label
The serious reply says "person" isn't an arbitrary label: it marks the kind of being whose life has special value, because it has projects, projects itself into the future and can lose more than pleasure by dying. Stronger protection falls on these beings, which would explain why killing a human is worse than killing a fish. Philosophically, this appears in Jeff McMahan's time-relative interest account.
- e
Why the counter-reply doesn't reach the conclusion
It changes the subject.
Even if killing a person is worse than killing an animal, it doesn't follow that killing an animal is permitted, still less for the pleasure of a meal.
It grades without giving a number.
Saying an animal's life is worth less requires saying how much less, and comparing it with what's gained in exchange. No one does that calculation when ordering a steak.
It still excludes babies.
The reply gives less protection to exactly the humans least projected into the future, and most people reject that consequence.
Suffering doesn't depend on personhood.
Even if accepted, the argument concerns death, not pain. Confining, mutilating and terrifying a being is still harm, whether or not it's a person.
The concept's history counsels caution.
"Person" has been denied to women and to enslaved people, and in each case the denial came after the practice it served to justify.
Reasoning errors
Logical
Is the form valid?
Definist fallacy
Equivocation
Proving too much
Non sequitur
Epistemological
Does the evidence support it?
Outdated empirical premise
Legalistic fallacy
Moral
Is the criterion coherent?
Label in place of criterion
Shifting the harm
Biases
Psychological essentialism
Makes "person" seem to name a natural essence rather than a category we created
Medin and Ortony, 1989; Gelman, 2003
Functional categorization
Animals classed as food lose the traits we associate with someone
In-group bias
"Person" works as the boundary of "us"
A common basis of speciesism and prejudice among humans
Status quo and legalistic bias
The existing legal category comes to seem the only possible one
A pattern in debates about extending rights
Motivated denial of mind
Denying personhood is a way of denying an inner life
Bastian et al., 2012; replicated by Jacobs et al., 2024
Extrapolations
The principle being tested is: "whoever isn't a person may be used".
If it applied to…Newborn babiesTap to see
They could be used. By the psychological criterion, a baby doesn't recognize itself over time or make plans, so it isn't a person
Whoever rejects this conclusion is admitting that sentience, not personhood, is what protects
If it applied to…People with advanced dementiaTap to see
They'd lose status as they lost memory and plans. The psychological continuity that defines a person gradually unravels
Medical practice and the law do the opposite and reinforce protection
If it applied to…Human groups already excluded from the categoryTap to see
Denying them the status of person would be enough to permit their use. This move has a history: women and enslaved people have been legally treated as non-persons
In each case, the denial came to justify a practice that already existed
If it applied to…Companies and riversTap to see
If personhood decides, companies would have more moral protection than a chimpanzee, because they're legal persons
Shows the label doesn't track the capacity to suffer
If it applied to…Artificial intelligenceTap to see
A system granted personhood by law would come to be worth more than a sentient being without it
Reinforces that personhood is a legal tool, not a moral criterion
Contradictions
Companies, foundations and, in some countries, rivers are legal persons with no sentience at all.
Many people treat their pet as someone, with a name, a personality and a will of its own, and deny this to the pig.
Babies and people with advanced dementia remain fully protected.
Punishing someone who tortures an animal presupposes that someone is being tortured, not just an object damaged.
"Isn't a person" is presented as a reason for treating it a certain way, when it really just describes the treatment already given.
What the argument gets right
What is true
The concept of person isn't philosophical rubbish. It captures something real: beings with self-awareness, memory of themselves and plans for the future may lose more by dying, and can be harmed in ways other beings can't, such as by humiliation or broken promises. Legal personhood is also a complex instrument, involving representation, procedures and responsibilities, and extending it requires careful institutional design, not just good intentions.
But
The mistake is turning this concept into the gateway to moral consideration. None of it answers the question that matters: is there someone there for whom what we do is good or bad? If there is, calling that someone a person or not is a decision about vocabulary, not about what we owe them.
Connections
Usually comes before
Usually comes after
Go deeper in Questão de Ética
Chapters from the open-access collection A Journey Through Animal Ethics that discuss this argument in more detail:
- Could the Possession of Capacities or Relationships… Vol. I, ch. 4
References
Provisional author-date format. The links indicate the sources checked in writing this chapter.
Philosophy
- An Essay Concerning Human Understanding, book II, ch. 27 (definition of person).
- Cavalieri, P., & Singer, P. (eds.) (1993). The Great Ape Project.
- The Ethics of Killing.
- Practical Ethics, on the distinction between human being and person.
Science
- Episodic-like memory during cache recovery by scrub jays. *Nature*, 395.
- Self-recognition in an Asian elephant. *PNAS*, 103(45).
Law
- Nonhuman Rights Project, Inc., ex rel. Happy v. Breheny* (2022), New York Court of Appeals; analysis in the *Harvard Law Review.
- *Te Awa Tupua (Whanganui River Claims Settlement) Act*, New Zealand, 2017.
- Estrellita case, dealt with in A7.