Philosopher Martha Nussbaum has been developing the capabilities approach to human well-being and rights for decades. The theory, which builds on the framework of Indian economist Amartya Sen, argues that it’s society’s duty to nourish our ability to lead fulfilling, healthy lives.

In her new book, Justice for Animals: Our Collective Responsibility (out January 3), the University of Chicago law and ethics professor expands that realm to animals. As Nussbaum writes: “Each sentient creature (capable of having a subjective point of view on the world and feeling pain and pleasure) should have the opportunity to flourish in the form of life characteristic for that creature.” Factory farms, zoos, pet breeders — as well as what humans can do to advocate for and protect animals — all fall under Nussbaum’s discerning lens.

In your book, you identify the qualities of wonder, compassion, and outrage as resources for helping people understand the ethical framework of animal rights. Do you see those as a trajectory?

I imagine a typical trajectory that starts with wonder: We get curious about animals and think how amazing they are, then look more closely. We see they’re not doing well in many cases. And in many of those cases, the bad situation is caused by human injustice. So then comes compassion. We feel they’re suffering, and it’s not their fault. And that leads into outrage. How outrageous it is that these pigs live in these horrible gestation crates where they can’t move.

Yet there’s been slowness to incorporate this outrage into laws that protect animals. How do you think the capabilities approach might bridge the gap?

The capabilities approach is meant to be very close to people’s own perceptions. If you live with a dog, you understand that the dog needs movement, company, attention, all these different things, all these different abilities. To turn that into law is the tricky thing. Now, we do have some laws that are good but underenforced. Let me start with dogs. We have these puppy mills that breed dogs in terribly substandard conditions, and they’re selling them at pet shops all over the place. The puppy mills themselves are pretty localized. Most are in Missouri, some in Iowa, but they sell all over the country. It’s a terrible torture for these dogs. But then they still look cute, and people don’t realize where they’re coming from. The problem is that the states in which these mills are making big profit have been unable to pass laws regulating these breeders. Then the states in which the puppies are sold have to take up the slack. Chicago has really been very proactive. The City Council passed a law [in 2014] making it illegal to buy a dog through a pet store unless you have evidence that it comes from a recognized shelter. Now, at first, that wasn’t enough because there were these bogus organizations that the puppy mill people set up. They were just fronts. So then Alderman Brian Hopkins got after that and he proposed an amendment, which passed [in 2021], saying that it would have to be regulated in very specific ways. So right now, Chicago has pretty good laws. But the problem is, people go to the suburbs if they think, Oh, I don’t want a mature dog, I want a cute little puppy. Now, some suburbs have good laws too, but it’s so piecemeal, right? What we really need is a statewide law about this.

You point out that it’s even harder to legislate for animals across national borders, since many animals migrate.

The really sclerotic situation here is to coordinate different nations that have different ideas of animal rights, different incentives in terms of industry and their greed for products. Whaling is my example. We do have an International Whaling Commission, but that was set up really by people who love the killing of whales but just thought we have to rein it in so the whales don’t all go extinct. The trouble is that practices are very well entrenched. And there are some nations, particularly Japan, where they use all kinds of bogus arguments to defend what’s going on. And then when they lose in court — and they have — they just withdrew from the International Whaling Commission. Whales are still being harpooned, not just by Japan but also by Norway and many other nations.

What about the idea of individual animals receiving standing in judicial systems?

Everyone says, “Of course animals can’t go to court, blah, blah, blah.” But the fact is, none of us go to court on our own unless we’re very foolish. We retain a lawyer. Then there are people who couldn’t even actively solicit legal representation, like those with severe cognitive disabilities, who still have standing to sue in court. Just because they’re human, they can be the plaintiffs in an action if they’re being abused. And so why shouldn’t this be the case for animals? There have been four countries that have given some legal standing to animals. The most fun one is Colombia, where Pablo Escobar brought a whole bunch of hippos. He just liked exotic animals, but he let them run wild. These hippos were running around and breeding quite prolifically, and people felt this was a nuisance at a certain point. Hippos are, in fact, very aggressive. [Colombia] decided to just go and shoot them all. And so a humane organization brought an action in the name of the hippos. So it says, you know, “Hippos of Such-and-Such against Colombia.” The U.S. did allow some expert witnesses to go testify in the Colombia case, and the court said, “We will recognize the role of these experts.” So that was a sort of end of the wedge, maybe, toward getting standing in U.S. courts. Someday this has got to happen. [Rather than killing the hippos, Colombia is now castrating the males to prevent breeding.]

In the field of philosophers and scholars working in the capabilities approach, do you see a growing consensus that animal rights is the next frontier?

It’s actually pretty controversial. There are people who think that human suffering takes priority, takes absolute priority. So unless we eradicate hunger, child poverty, and so on, we shouldn’t even think about the situation of animals. One time when I gave a plenary address on the sufferings of animals and what we should do about it, I heard later that people were saying, “Oh, has Nussbaum given up on human suffering?” I actually think, first of all, the whole natural world is really part of our human apparatus of concern. We’re living more narrowly as human beings if we don’t awaken ourselves to the world around us. So that’s part of my answer. But the other part is, it isn’t an either-or. Reducing human suffering and reducing animal suffering involve many of the same issues. That is, preserving natural habitats, trying to deal more responsively with issues of the corporate attempt to manufacture food that isn’t really healthy. The food that’s produced in the factory farm industry is actually not very good for human beings. So we would all be better off if some of these reforms were enacted. I see no reason that they’re in competition with trying to end human poverty.