QuestionsDo animals matter as much as we do?Justice is owed to every sentient animal: it must be able to flourish in its own way
Do animals matter as much as we do?They have rights

Justice is owed to every sentient animal: it must be able to flourish in its own way

The capabilities approach applied to animals; justice for animals

Martha Nussbaum born 1947She studies emotions, love and the fragility of the good life, and reads Plato's Symposium with attention to individual persons.
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What it claims

Justice is owed to sentient animals: the law must protect their flourishing and give them legal standing.

Why

Every sentient animal strives to live well in its own way; injustice is thwarting that striving, and animals cannot defend themselves.

The same idea through history
Aristotle335 BCAristotle: each living thing has a way of being proper to its kind, and the good is to carry it out. Nussbaum extends this idea of flourishing to all animals, beyond the human.
Jeremy Bentham1789Bentham: the question is not whether they reason, but whether they suffer. Nussbaum keeps sentience as the line, but refuses to count only pain.
Martha Nussbaum2006Frontiers of Justice (2006), chapter on justice for nonhuman animals: first version of the capabilities approach applied to animals. Justice for Animals (2023) develops it.
In short

"Justice is owed to every sentient animal: it must be able to flourish in its own way" is an argument by Martha Nussbaum (Justice for Animals, 2023; Frontiers of Justice, 2006, 2006) on the question "Do animals matter as much as we do?" (answer: they have rights). Its claim: Justice is owed to sentient animals: the law must protect their flourishing and give them legal standing. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P5). AskPhilosophy presents 3 objections, 3 of them with a documented reply, and the original text behind each premise, checked word for word.

Justice for Animals, 2023; Frontiers of Justice, 2006
Valid with an implicit premise

For Martha Nussbaum, the question is not only to avoid making animals suffer. Each animal strives to live well in its own way: to move, to eat, to live in a group, to play, to act. There is injustice when this striving is wrongly thwarted. She draws the line at sentience, like the utilitarians, but refuses to look only at pain and rejects the idea of a ladder of nature with humans at the top. Since animals cannot defend their interests before a court, she asks that they have legal standing and representatives.

P1Every sentient animal is a being that strives to live well, in the way proper to its kind. The capabilities list describes this shared terrain: a vulnerable, striving animality that each species inhabits in its own way.
P2Injustice is the wrongful thwarting of a sentient creature's striving to live well. It does not matter whether it resembles us: it counts for what it is.
P3Human practices massively thwart this striving in animals, in ways nothing excuses.
P4Animals cannot defend their own interests. They therefore need a political voice: legal standing and representatives, as for humans who cannot speak for themselves.
P5 · implicit premiseAn injustice that strikes beings unable to defend themselves calls for the protection of law, not only the goodwill of individuals.
Justice is owed to sentient animals: the law must protect their flourishing and give them legal standing.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P5, the computer finds a world where animals are wronged and humans choose to be kind as a private virtue, with no law. The other premises are true, but the conclusion about legal standing is false.
Valid with P5. Without it, we only know that animals suffer an injustice and would need a voice if they were protected. Nothing says that law should do it. P5 is the step from morality to law: for Nussbaum a just society is measured by what each being is able to do and to be, which only law guarantees. This is the point disputed by defenders of individual benevolence.
Analogy. A mistreated child cannot file a complaint: an adult does it for him, and the law gives him that right. Nussbaum says it is the same idea for animals. Her opponents say a child will become an adult who takes part in society, which an animal never will.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

Peter Singer 1974 · attacks premise 2

For Singer, sentience, the capacity to suffer or experience enjoyment or happiness, is the only defensible boundary of concern for the interests of others. It is enough to give equal consideration to the interests of all sentient beings; a long list of capabilities is not needed.

a defender replies
see the argument
Martha Nussbaum defender of the argument · 2020
Nussbaum answers that utilitarianism does zero in on pain, a key issue in our exploitation of animals, but that it flattens the world too much. A utilitarian such as Singer, she says, cannot articulate the many different things animals need in order to live well.
Where the debate stands (our summary)The two camps agree on sentience as the limit. The disagreement is over what matters for an animal: only pleasure and pain (Singer), or also movement, company, play, agency (Nussbaum). Singer rejects the idea that these goods have a value apart from their effect on well-being.
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Jan Narveson 1977 · attacks premise 4

For Narveson, a contractualist, rights are rules that beings able to understand them accept among themselves out of mutual interest. Animals cannot take part in this contract or claim rights themselves: this is his "rational egoism", set against Singer and Regan.

a defender replies
Martha Nussbaum defender of the argument · 2022
Nussbaum answers that this does not remove animals' need for a political voice. She holds that it matters that animals have a political say, which means for her legal standing and legal representation, as for humans who do not speak for themselves.
Where the debate stands (our summary)Core point: does justice come from an agreement between equals capable of reciprocity (contractualism), or from the vulnerability of any being striving to live well (Nussbaum)? The debate also concerns very dependent humans, whom both camps want to protect.
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Jeff McMahan 2010 · attacks the conclusion

Jeff McMahan, in "The Meat Eaters", argues that if animal suffering matters, the suffering caused by predators matters too. We would then have reasons to wish for the disappearance of carnivorous species, if it could be brought about without causing greater harm. He adds that with our present knowledge, it would be unwise to try.

a defender replies
Martha Nussbaum defender of the argument · 2020
Nussbaum answers that, where wild animals are concerned, we do not know enough about them to intervene very much, and that most of our interventions would probably be harmful.
Where the debate stands (our summary)A practical rather than theoretical disagreement: McMahan and Nussbaum both admit that wild suffering matters, but disagree on when ignorance makes intervention imprudent.
What today's voices say
Defend it
Martha NussbaumHer own argument: every sentient animal strives to live well in its own way, and thwarting that striving is an injustice.