A Philosopher’s Guide to an Ethical Diet: A Conversation With Peter Singer

Humans have an enormous impact on planet Earth, but from both an animal welfare and an environmental perspective, perhaps nothing is more important than our diets.

In 2022, more than 82 billion livestock animals were slaughtered for meat, according to the Food and Agriculture Organization of the United States, with the majority of those animals being factory farmed. In addition to enormous animal welfare implications, the practice of farming animals is estimated to account for somewhere between 11% and 20% of all greenhouse gas emissions.

All things considered, what is the most ethical diet? According to utilitarian moral philosopher Peter Singer, it’s one that includes zero — or at least very few — animal products.

Singer is among the most influential living philosophers and is widely credited for putting animal ethics on the map with his controversial 1975 book, Animal Liberation. Because most nonhuman animals have the capacity to suffer, Singer argues, we should not exploit their suffering for our own good, particularly with the horrific conditions of practices like factory farming.

^{Peter Singer at his office in Princeton University on Sept. 22, 2022. Derek Goodwin Photography}

More recently, he published an extensively revised version, Animal Liberation Now, which brings to light the brutal living conditions for tens of billions of animals today.

I recently had the pleasure of interviewing Singer and discussing speciesism, the conditions of factory farming and how to have an ethical diet.

You’re widely regarded as the father of the animal rights, or as you may prefer, the animal liberation movement. Can you make your case for the pursuit of animal liberation?

The case for the animal liberation movement is that to disregard or discard the interests of beings because they’re not members of our species is indefensible. I use the term “speciesism” to describe that, and that is intended to make the parallel between other -isms such as racism and sexism that most people — certainly I hope the audience that I’m addressing — reject and say that although the analogy is obviously not complete, in all of these cases there’s been a dominant group which has developed an ideology to enable it to justify using a group that it dominates. In one case, nonwhites, in another case, women, and then in this case, nonhumans. To justify using that group for its own purposes in ways that are clearly very harmful to the group, but somewhat beneficial to the dominant group.

So I think we ought to be able to see that the difference in species is not relevant to how bad it is when a being is suffering, if the being is capable of suffering. What matters is how much the being is suffering, what kind of suffering that is — can we compare it with the suffering that we humans may experience? To some extent, I believe we can. And when we make that comparison, it’s not difficult to see that there are many areas in which we inflict immense suffering on nonhuman animals for either no benefits or minor benefits to humans. So I think it follows from the idea of equal consideration of similar interests — which is a principle that I think should hold irrespective of species — it follows from that that many of the things we do to animals are unjustifiable, and that’s the case for animal liberation, or if people want to so put it in terms of recognizing the rights of animals, or, I would say, the case for equal consideration for similar interests across species.

Should we all become vegan or vegetarian?

I would say not in absolutely all circumstances, but if we’re thinking about the situation of somebody who has the option of nourishing themselves well, having an adequate diet, being healthy without consuming animal products, and if those animal products come from commercial enterprises where there’s a profit motive for not being concerned about the wellbeing of the animal beyond productivity of the enterprise, then I think it does follow that we ought not to be consuming those products. 

So as I say, there are various other circumstances — that would be circumstances of people who can’t nourish themselves adequately without eating animal products — they have a much larger sacrifice to make than others. And there may be cases where you’re not getting your animal products from large commercial enterprises where the animals have good lives and are humanely killed that would need separate consideration, but the claim I make is one that obviously applies to billions of people in the world today, so that’s enough, I think, to try to get that changed.

You first published Animal Liberation in 1975. And then in May of 2023, you published an updated version, Animal Liberation Now. Surely, much has changed in terms of factory farming practices, the state of animal welfare, among many other factors. In your view, what are some of the most significant changes since 1975, and what made you decide that it was time to publish a revision of Animal Liberation?

Obviously there has been a lot of changes and that’s why it’s really virtually a new book, rather than just a new edition because I’d say probably about half of the text is new. And not so much on the philosophical argument that I just gave you. I think that that has stood up very well to criticism and discussion. But the two longest chapters of Animal Liberation are largely factual where I’m describing research done on animals, and the other describing factory farm conditions. Those chapters had to be completely rewritten. And then there were other discussions about climate change, for example — which was not on my radar or not on many people’s radars in 1975 — had to be brought in because that’s very relevant to the ethics of eating animal products. And I wanted to talk a bit about the progress that the animal movement has made and the progress that it has not made. So those are important changes to the book, and I wanted to talk about that — the new discussion about ethical questions relating to animals, which again was very much a neglected issue, hardly an issue that anybody touched upon in 1975, but now has quite a major literature. So a lot of different things. And also, I should add, there’s more research on animal sentience. So I think we can have more confidence in saying that fish, for example, are sentient, which is something that some people questioned after the first edition was published. And the sentience of octopuses, and even some crustaceans, like lobsters, I think is now much more firmly established than it was. So there’s been a lot of science that has supported the view that I was taking about animal sentience and actually has extended it.

^{Peter Singer with a previous version of Animal Liberation, on Sept. 22, 2022. Derek Goodwin Photography}

In terms of the most significant changes, well, I think some things have gotten better and some things have gotten worse. I talked about the improvements in regulation of factory farming in a few places, most notably the European Union. Also some states of the U.S., but only a minority, particularly California, which passed stricter legislation. So those are good things, but there have also been negative developments. In the case of the chicken industry — chickens are, by far, the most numerous of the land-based vertebrate animals we raise for food — that’s gotten worse because chickens have been bred to grow even faster. And this causes all sorts of problems for them and causes skeletal abnormalities. And they put on weight so fast now that their legs are immaterial for bearing their weight. Chickens are slaughtered when they’re very, very young birds — about six weeks old when they’re slaughtered. And so they’re really babies and their leg bones just aren’t strong enough to support the weight that they’ve put on because they’ve been bred to eat so much and grow so fast. So there’s actually a new cause of pain to bear. They have difficulty bearing their weight, difficulty standing up and walking around because of how fast they’ve been bred to grow. So there are new developments, like that, that make factory farming even worse in some respects than it was.

You describe yourself as a flexible vegan. So you must believe that there’s at least some wiggle room when it comes to having an ethical diet.

That’s because, you know, my ethics are utilitarian or consequentialist. I’m always looking at the consequences of what I do, and my ethics is not about rigid rules. So for me, being vegan is not like somebody — a religious person — who will only eat halal or kosher meat and will think it doesn’t matter how much non-kosher or non-halal meat you eat. It’s just wrong to do it and the wrong would be as great if you ate more of it or less of it. But for me, I want to not be complicit in supporting these industries that treat animals so badly. And the degree of complicity obviously varies by how much I’m spending — to what extent my dollars are supporting those industries. So if for most of my everyday shopping, I avoid animal products, but sometimes when I’m traveling there’s nothing much to eat that doesn’t have some, you know, something like a dairy product, let’s say in it. It’s not a significant contribution that I’m making, and if it’s going to be really difficult for me to get anything to eat that doesn’t contain an animal product — or if I’m in social circumstances where it would disturb the group if I said no, I can’t eat anything here — I’ll eat something that’s vegetarian but not vegan. So that’s the sense in which I’m flexible.

So for people who recognize the cruelty of factory farms and the climate implications of factory farms, and even the climate implications of organic animal farms, but don’t feel ready to commit fully to veganism or vegetarianism, how can those people eat more ethically?

Well, they can still avoid factory farmed products which I think is really important, because that’s where the vast majority of the suffering we inflict on nonhuman animals is. So I would say, depending on how much you feel you want to eat in terms of animal products, I think if you’re talking about the most affluent countries, including the United States, the animal product that perhaps is most easy to get in a form that is not ideal, but is still acceptable, would be eggs from pasture-raised hens. So if you can find a farm that is producing eggs, and the hens really are out on pasture — it’s not just that they’re cage-free, which still might mean that they’re locked up in a big shed — but they’re actually able to go outside and exercise, chase insects, dust bathe, all of those things that are natural for the hens, then you could at least say, well, if the hens are having a reasonably good life here (and sure they’re going to get killed prematurely, and sure the male chicks of that breed are going to get killed immediately on hatching because they’re of no commercial value), it’s a better product definitely than products from animals who are inside all of their lives, very crowded. So I would start with that.

After that, it does get harder. Many people will say, well, what about dairy products from organically raised cows — cows who are outside on pasture again. And that’s certainly better from an animal welfare point of view — as for that matter is beef from grass-fed cows — but it’s worse for the climate, because cows are ruminants and they emit a lot of methane. And the fact that they’re on grass doesn’t really help in terms of reducing their methane output. It’s still there. And in fact, some studies suggest that with grass-fed beef, it’s actually higher, because if you don’t feed them on grain as most beef is fed, for at least the last six months of their lives, they put on weight more slowly, and so for each pound of beef produced there’s more digesting and more methane produced. So you know, that’s a dilemma. But again, if people say, well, I just want to do this occasionally as I need it, or I’m not prepared to go without it, maybe eating small quantities of grass-raised or pasture-raised dairy or beef products might be the next thing to do.

I understand that you’ve recently stepped back from your teaching role at Princeton. So if you don’t mind sharing, what’s next for you?

Yeah, you’re right, I taught my last semester at Princeton now but I’m I’ve got plenty of opportunities to write, to speak, to give interviews like this one. And I’ve got offers of taking visiting positions in other parts of the world which I plan to do, the first of those probably going to Singapore for about a month during 2024. There are other possible places that I will be going to and speaking out in Europe and possibly in Asia. So yeah, I’m planning to keep pretty busy.

That’s all the questions that I had prepared for you. But I’d also like to ask if there’s anything else you’d like to share? Maybe something that we haven’t touched on that you’d like to add?

Oh, I think we’ve covered quite a lot. Obviously, I have a broader interest in bioethics beyond what we’ve spoken about. And so there are a variety of things I’m interested in and I’m continuing to work with the organization The Life You Can Save, which tries to encourage people to give to the most effective charities helping people in extreme poverty. So I think that’s also an important thing to do. And if people want to know more about my work there, they can have a look at my website, petersinger.info, or also go to thelifeyoucansave.org where they can download a free digital copy or audio copy of my book The Life You Can Save and learn more about my work for people in extreme poverty.