Jeff McMahan is an Oxford moral philosopher and vegetarian of almost 50 years. He still doesn’t know if it’s wrong to eat meat.

I discovered this when I called McMahan in June to discuss his recently delivered lecture, “Might we benefit animals by eating them?” The lecture examined whether it can be good for animals to be brought into the world even if they’re reared to be killed and eaten. On the phone, I was confused when McMahan said he intuitively disagreed with his own ethical arguments in favor of eating meat. Was he or was he not against eating animals that had been raised humanely?

He paused: “That’s what I’m trying to figure out.”

McMahan said he’d found some flaws in his old arguments on the subject, and was retracing his logical steps. He hoped to find a reason to support his intuitions, but he was open to changing his mind. “This is what a philosopher’s supposed to do, follow the argument wherever it leads,” he said. “You’re supposed to follow it even if it leads somewhere you don’t want to go.”

Most of us are not like McMahan. We do not follow moral arguments if they lead to uncomfortable conclusions. We prefer to make ethical decisions based on instinct, popular wisdom, and whatever feels like the right response to a particular situation. It’s a mushy process—one that moral philosophers attempt to de-mush by laying out the myriad assumptions and implications that are weaved into almost every human action, from how we spend our money to our relationships with family.

Humans are so immersed in immorality that we can be entirely unaware of it.

Why bother with moral philosophy when common sense serves most of us perfectly well? The simple answer is that, as history shows, commonsensical beliefs are very often wrong. Slavery, marital rape, and bans on interracial marriage were all widely accepted in the relatively recent past. Much like fish who, as the proverb goes, are the last to discover water, humans are so immersed in immorality that we can be entirely unaware of it.

Part of a moral philosopher’s work, then, is to question common sense and reveal our ethical blind spots. “I do think we make moral progress in part by challenging our intuitions,” McMahan said.

This process is not as straightforward as using reason to override moral instincts. (When are philosophical processes ever straightforward?) Though our intuitions are very often wrong, they’re nevertheless necessary to give morality its meaning. If we have no emotive response, if no one cares at all when an act of evil is committed, then morality does not exist.

And so rational thinking and moral instinct are in a constant state of slippery conflict. As I discovered through my conversations with McMahan, there’s no neat solution to this problem; no formula that reveals what’s truly moral. But his struggle to figure out whether it’s wrong to eat meat offers a deeply personal, imperfect blueprint of how to make an ethical decision.

The life, and intuitions, of an ethicist

More than 10 weeks after I first spoke to McMahan, I went to visit him at his study in Corpus Christi College at Oxford University, to see how he’d progressed in his ethical workings. The dark-wood paneled room, lined with somber tomes bearing such impressive titles as The Theory of Good and Evil (in three volumes) and The Methods of Ethics, seemed the ideal setting for a philosopher to unpack his latest conundrum. But McMahan said he was still stuck on the problem of meat-eating, having procrastinated by working on self-defense issues instead.

“I’ve haven’t done much on killing animals,” he said, as he poured boiling water he’d distilled himself over tea leaves that had been sent to Oxford from the Himalayas, freshly picked the month before. “I’ve been too focused on killing people.”

He didn’t smile or acknowledge that this was a joke, but he still managed to project a certain awkward warmth. McMahan looked more like a corporate figure than a typical scruffy professor, with a buttoned-up light blue shirt, navy trousers, and neat grey hair. At 62 (on the cusp of 63 when we met), his eyebrows were habitually lowered, making him appear glowering except for when his face transformed, briefly and unequivocally, into a surprisingly joyful smile.

In many ways, McMahan lives up to the archetypal figure of an eccentric academic.

Despite his stern manner, McMahan seemed glad to have company. When we’d arranged a date to meet, he’d said he was free at any time on any day—he had no conflicting meetings, only a never-ending pile of solitary work. Though McMahan’s philosophy is explicitly focused on practical ethics with real-world relevance (as opposed to more abstruse topics such as meta-ethics or normative ethics), his routine is far removed from the crowded, fast-paced reality of many people’s everyday lives.

“A day in my life is very boring,” he said. He wakes at 9.30 am, has a piece of fruit for breakfast, and immediately begins to work. His only breaks are a salad for lunch and granola from the university dining hall for dinner. Sometimes he goes to Corpus Christi; sometimes he works at home all day. He stops at 11.30 pm or midnight, has a bath, reads a biography or novel, and then goes to bed. He lives alone.

McMahan doesn’t go on vacation, as he’s “overcommitted, overworked.” Any hobbies? “I listen to music and I play squash and tennis,” he said, though, “I don’t have enough time or enough partners.” Most of his friends are philosophers and, though he seldom has dinner out, he does go to the odd social event. “I do have friends I meet at the pub,” he said. “I enjoy a meeting at the pub in the evening. I can work until close to closing time.”

In many ways, McMahan lives up to the archetypal figure of an eccentric academic. Immersed in his work, he fulfills the professorial stereotype of someone who’s slightly removed from the rest of humanity. Perhaps his lifestyle is unimportant. But then again, surely we develop our moral instincts—right or wrong—through our personal lives and relationships.

At one point in our conversation, McMahan referred to contemporary society’s wariness of intellectuals. “These people are really contemptuous of academics in particular, and the whole idea that there are experts and expertise and we can have specialized knowledge about things,” he said.

He’s right, of course: Widespread suspicion of experts is unwarranted and foolish. But on the other hand, it’s possible that those who view academics as cloistered and out of touch may also have a point. Perhaps wholly dedicating oneself to a life of the mind can create idiosyncratic moral intuitions. Just as we must all interrogate how our personal backgrounds shape our instincts, surely professors should question how a life spent in the ivory tower might affect their decisions.

Taking moral logic to its extremes

Philosophers’ attempts to unravel our moral instincts often lead to bizarre, if highly logical, academic arguments.

Reuters/ Andrew Cullen Is it ever okay to eat meat?

Consider the problem of whether it can ever be morally acceptable to eat meat. For McMahan, the answer hinges on whether humans can offset the wrongness of killing a chicken or a cow by providing the animal with an enjoyable life in the first place.

“Overall, the ostensible victim is being benefitted by the practice as a whole and would never exist were I not able to kill it at the end,” said McMahan. He referred to 19th-century philosopher Leslie Stephen, who wrote in his 1896 book Social Rights and Duties, “The pig has a stronger interest than anyone in the demand for bacon. If all the world were Jewish, there would be no pigs at all.”

This argument does not engage with the environmental impact of humanely raising animals in order to eat them. Instead, it’s focused entirely on whether the act of killing itself can be justified. The question still holds practical relevance, according to McMahan, because it connects to one of the fundamental issues in moral philosophy: The non-identity problem.

McMahan, and several other contemporary philosophers, consider the non-identity problem to be the greatest unanswered ethical question. It was first identified in the early 1980s by moral philosopher Derek Parfit, a close friend of McMahan’s who died on the first day of 2017.

“The pig has a stronger interest than anyone in the demand for bacon.”

The non-identity problem runs as follows: Humans are capable of actions that simultaneously create an objectively worse state of affairs, but also allow certain people (who otherwise wouldn’t have existed) to be born. For those who exist as a direct result of such actions, the original act is not bad for them. It’s unclear whether the act is, in fact, bad for anyone. This problem brings several deep moral intuitions into conflict.

For example, when it comes to eating meat, of course animals would be happier if they were free to roam and never killed. But humans are motivated to bring many animals into the world in order to kill and eat them. Those animals simply would never exist in the first place were they not to be used as food—so perhaps it’s better for them to exist and die than never be born?

On a broader scale, if we continue to follow the current policies on climate change, people on earth will have far worse lives in the coming centuries. If we drastically change our policies, then everyday behaviors and lives will be transformed as a result. “People will meet different people, marry different people, children will be conceived at different times,” said McMahan. “In 100 to 200 years, if we follow the status quo policy, one set of people will exist and be badly off but still have lives that will be worth living. If we follow other policies, a different set of people will exist and have better lives.”

This may seem like an easy problem to solve: Simply go for whichever act leads to the existence of more better-off people! But such a solution is known in philosophy as “the repugnant conclusion.” It implies that we have a moral duty to simply create as many basically happy people—or barnyard animals—as possible.

That sounds wonderful, right? But it’s not clear when this moral imperative stops. It suggests that we should create the maximum total happiness possible, meaning that a massively overcrowded world of people with barely satisfactory lives would be preferable to a world with a much smaller population of decently happy people. In addition, it implies we’re morally obliged to be constantly breeding.

McMahan is not certain whether the non-identity problem will ever be solved. “People have been trying to do that for a very long time,” he said.

Does philosophical logic make sense in everyday life?

The calculated logic that dominates philosophical thinking also seems to infiltrate McMahan’s personal life. He’s stoical in conversation, and lacks the reflexive defensiveness that leads most people to protect their self-image. I asked whether his wife, from whom he’s separated, would consider him moral. “Yeah,” he said, with a slight note of uncertainty. After our meeting, he sent a follow-up email that said his views on the subject were “largely worthless” and included his wife’s email address so that I could ask her directly.

“It made me understand how some people do things, like kill people, and they don’t mean to at all, it just happens to them.”

I wrote to his wife, who told me she didn’t want to talk. She’s kind, but uncomfortable with the idea of weighing in. This is perfectly understandable; many of us might be perturbed to be asked to comment on our former partner’s morality. Though McMahan’s suggestion seems ethical in the abstract, it lacks a certain sentimental intuition.

McMahan showed a similar emotional remove when I asked him to recall a time that he’d acted immorally. After struggling to drudge up a memory, he remembered—with great surprise—that he’d recently lost his temper at a picnic, shattering a plastic plate filled with food. “It amazed me so much. It made me understand how some people do things, like kill people, and they don’t mean to at all, it just happens to them,” he said. “It didn’t seem like intentional action to me. It was like it happened to me.”

He’s largely learned to suppress his anger, an emotion that he considers counter-productive. Does he suppress other feelings? “Yeah. A lot of them,” he said. Plenty of emotions, after all, can be hurtful to others. “I’m justifiably sad an awful lot,” said McMahan. “I don’t want to burden people with my sadness.”

He didn’t sound self-pitying, or even lonely, when he said this. His hyper-rationality seems to make him view his actions and inner life with a degree of remove—as if he watches himself from a far-off, objective perspective, as just another figure navigating the strange moral scenarios of the world. Clearly, his feelings and relationships are dominated by his intellectual thoughts. Does this make him better than the rest of us, or simply different? It’s not certain whether he’s living the moral life we should all aspire to, or one that, if adopted by everyone, would tear apart the fabric of society.

Everything’s personal

Though McMahan’s philosophical studies focus on clear-cut arguments, it’s impossible to shed personal preferences. Lurking behind this formal discussion of killing humanely-reared animals lies McMahan’s decision to go from being a hunter in South Carolina to a committed vegetarian. He made the choice as a teenager, after he saw a man wound a bird on a dove shoot.

“I thought that if I wasn’t willing to kill these animals in order to eat them, I shouldn’t pay other people to kill them for me.”

“I remember this man walking in such a leisurely way towards this bird that was flapping across the ground trying to evade him,” he recalled. And so McMahan sold his gun and stopped hunting. A little later, his “first philosophical thought” turned him vegetarian: “I thought that if I wasn’t willing to kill these animals in order to eat them, I shouldn’t pay other people to kill them for me,” he added.

Even when dealing with abstract ethical scenarios, individual intuitions are unavoidable. At one point in our conversation, McMahan said creating a world where people had incredibly short lives filled only with the highest pleasures would be preferable to a world where people had long but barely pleasurable lives. Neither option sounds particularly pleasant to me: A wonderful life seems to count for very little if it only lasts for two hours.

The scenarios up for ethical debate tend to get very weird, very fast. In the course of our discussion about the non-identity problem, McMahan raised, for serious consideration, the possibility of creating genetically-modified brainless animals; bringing children into the world on the condition that they must die and donate their organs when required (“it’s puzzling” why this is considered acceptable for animals but not humans, he added); and why humans definitively have greater happiness than dogs (humans have longer lives, experience “psychologically unified” narratives, and can access “dimensions of well-being” such as achievement, knowledge, and great love, that dogs cannot.)

These thought experiments sound, out of context, like the ridiculous playthings of philosophers who have no grip on how morality affects most people. But following the logic of moral arguments to their far-fetched conclusions also reveals their flaws, and McMahan takes such ideas very seriously indeed.

It’s a mistake to assume that philosophy stays within its ivory tower.

Though the conversation takes some wild turns, the non-identity problem could potentially shape our moral understanding of eating meat, abortion, climate-change policies, procreation, and population control. McMahan said it’s a mistake to assume that philosophy stays within its ivory tower. In the US and UK, “you’ll see the effects of the implementation of ideas about people’s rights, property rights, particular freedoms of speech, ideas that are traceable to the works of John Locke, John Stuart Mill,” he said. In the past 50 years, political philosopher John Rawls’ work on what constitutes an egalitarian society changed the contemporary conception of a just democracy; utilitarian Peter Singer convinced thousands of the importance of animal rights. Meanwhile, The Trolley Problem—an ethical conundrum that explores the moral competition between actively doing versus allowing harm—is about to be played out on a massive scale through self-driving cars.

And so, for someone like McMahan, the question of whether it’s okay to eat meat isn’t just an interesting thought exercise. Solving the non-identity problem is, quite literally, an issue of life or death.

The pitfalls of rational reasoning

Philosophers tend to believe that we can think our way to a moral answer; that logic and careful reasoning are enough to show us the truth. But given that human values are so tied up with our intuitions, perhaps an overly rational approach can lead us down an unethical road.

AP Images/ Robert Sciarrino Anna Stubblefield’s conviction has been overturned.

I saw a clear-cut example of reason’s shortcomings when I brought up a New York Times article that McMahan co-wrote with philosopher Peter Singer on the Anna Stubblefield case. Stubblefield, a former professor of ethics at Rutgers University, said she’d fallen in love with a mute man with cerebral palsy (known in court records as DJ.) She claimed she’d talked with him through “facilitated communication,” a controversial technique that is supposed to allow nonverbal people with disabilities to type, and that the two had sex.

In 2015, Stubblefield was found guilty of rape, on the grounds that DJ was not able to consent. This conviction was overturned in June, and Stubblefield is now awaiting a second trial.

In the Times op-ed, Singer and McMahan argue that DJ’s cognitive abilities may not actually be impaired. But they also appear to imply that nonconsensual sex with people with cognitive disabilities is not immoral. They write: “On the assumption that [DJ] is profoundly cognitively impaired, therefore, it seems that if Stubblefield wronged or harmed him, it must have been in a way that he is incapable of understanding and that affected his experience only pleasurably.”

I’m used to controversial, unpleasant ideas in philosophy. But I told McMahan that this conclusion seemed unsupported by a philosophical argument. McMahan said that he “had a word limit,” so was not able to explain as fully as he would have liked, and that everything in the piece was intended to apply only to the Stubblefield case—and not other instances of sex with those who are cognitively impaired.

Despite the sensitivity of the subject matter, he was truly surprised and hurt when the article generated a fierce backlash. “No one among the people who criticized us harshly seemed to have the least compassion for a thoroughly decent and indeed admirable woman who was sentenced to 12 years in a New Jersey prison,” he said.

McMahan emphasized many specific details of the Stubblefield case: If DJ was cognitively impaired, he still had a mature male body capable of experiencing pleasure, and Stubblefield believed she was doing what he wanted rather than exploiting him (both details, in McMahan’s view, alter the morality of the act.) But he also seemed to suggest that sexual assault is only traumatic if the victim intellectually understands the concept of sexual violation.

As any psychologist will tell you, plenty of experiences that we don’t understand or consciously remember have massive effects on our psyches.

“If you had an infant, let’s say a two-day-old infant that can’t even recognize a human face, doesn’t know what a human being is, much less have a concept of sexual violation or sexual integrity or anything of the sort,” said McMahan. “Suppose that this is an anomalous infant that can have erections and orgasms. That can be a different case. If somebody thinks, ‘Ah, this is an infant that can have erections and orgasms, let’s give it erections and orgasms, that must be pleasant for it,’ then I don’t think that that individual, becoming a person and having no memory of this, is going to be affected by that.”

To me—and to many readers of the Times article—this argument makes little sense. McMahan has no evidence that such a two-day-old infant would not experience trauma. He seems unreasonably confident that it’s necessary to logically understand the nature of sexual violations in order to experience them as violations. But, as any psychologist will tell you, plenty of experiences that we don’t understand or consciously remember have massive effects on our psyches.

McMahan was clearly not persuaded by my objections to his argument. Meanwhile, I realized that my counter-argument was as much opposed to his theory’s seeming lack of moral instincts as to its weak reasoning.

When I first spoke to McMahan, the notion that a strong logical argument should be enough to override moral intuitions struck me as noble. But our discussion about the Stubblefield case made me realize that, even if presented with a perfect argument (which McMahan did not make), I would be reluctant to abandon the intuition that sex with someone who has the mind of an infant is always wrong.

A matter of instinct

Though moral instincts are personally invaluable, the strength of a philosophical argument depends, almost entirely, on its logical structure. McMahan is still working to find that structure when it comes to the meat-eating question. But he has already decided its conclusion.

He made his decision after reading a Boston Review article in which a Buddhist man describes humanely raising, then killing and eating, pigs. The descriptions portray the pigs as social, intelligent creatures, with pleasures in their lives and real relationships with humans. “There are these moments of insight where he says, ‘This seems wrong to me,’” said McMahan. “And then he just killed them.”

Though he hasn’t finished thinking through the theoretical reasoning, one man’s description has persuaded McMahan that rearing and killing animals is not ethically permissible. Having started our conversation with McMahan stressing his willingness to abandon moral intuitions, we end it with his acknowledgment that, really, you can’t do moral philosophy without them.

“Intuitively, whatever the arguments are, reading the article had that effect on me. I was so glad I read it,” said McMahan. “I thought, ‘Now I know.'”

Our instincts can lead us astray. But nothing would truly matter were it not for our deeply-felt, potentially irrational, emotional responses. The problem that McMahan and moral philosophy must face is how to integrate such intuitions into a solid theory. And for those of us facing ethical decisions in everyday life, we must tackle the same potentially unanswerable questions as McMahan, testing both our intuitions and our logic.

No great ethical conundrum can be answered in a way that appeases all moral philosophers—or all people—easily. But by carefully thinking through the self-doubt, logic, and instinct bound up in morality, it’s certain that, at the very least, the decisions we reach won’t be shallow.

It’s difficult work, and slow. McMahan plans to spend several days working solidly for 12 hours at a time on the question of meat-eating, reading others’ work and writing constantly. That’s just the beginning. “And then,” he said, “you just have to sit and think about it for a terribly long time as hard as you can.”