Home / C. Nature, biology and evolution / Part DIR
"It's natural to eat meat."
something being natural doesn't tell us whether it's right. Nature also produces disease, infanticide and war, and we correct nature all the time with medicine, glasses and laws. Besides, what is called natural here has nothing natural about it: animals bred to grow fast, confined and slaughtered on an industrial scale. The argument describes our species' past and presents it as a moral rule for the present.
Note: this chapter doesn't discuss whether humans can digest meat, which is true. It discusses whether that makes eating it morally acceptable. The nutritional question is left to family G.
Short answer
Being natural doesn't make something right. Nature also has disease, infanticide and the strong dominating the weak, and no one uses that as a moral rule. We use medicine, glasses and anesthesia, which aren't natural, and we think they're great. Besides, supermarket meat comes from animals genetically selected to produce more, confined and slaughtered on an industrial scale, which is nothing like natural. Being able to eat meat is one thing; needing to and having to are others.
For children
All sorts of things happen in nature. Some animals steal food from others, fight, or leave the weakest behind. Does that mean we can do the same? No. We learned to look after people who get sick and to share with those who have less, and that doesn't come from nature, it comes from thinking about what's fair. Eating animals may have been natural once, but today we can live well without hurting anyone.
"If being natural makes something right, are C-sections, vaccines and glasses wrong?"
Como pode aparecer
"It's natural; it's always been this way."
"It's part of human nature."
"We're predators."
"Your ancestors didn't survive on lettuce."
"Are you going to go against millions of years of evolution?"
"We have canine teeth and an omnivore's gut." (which is C3)
"Meat made our brains grow." (which is C5)
"Meat-eating is a species adaptation, and adaptations aren't moral vices."
"I just follow what my body asks for." (which is C11)
The strongest version
"Eating meat is natural. Humans have always eaten it; it's part of our nature."
Strongest version (steelman):
- P1Humans evolved as omnivores, and eating meat has been part of our species' history.
- P2Behaviors that are part of a species' nature are legitimate for members of that species.
- CSo eating meat is legitimate for humans.
P1 is true. All the weight rests on P2, which makes a move philosophy has examined since the eighteenth century: from a description of how things are to a norm about how they ought to be.
The argument is valid. Its soundness fails at P2, which no one applies consistently, and in the word "natural", which changes meaning along the way.
Full answer
- a
Reconstruction and diagnosis
The argument is the best-known example of the appeal to nature: treating the natural as good and the unnatural as bad. It also runs into what is called Hume's law. David Hume observed, in 1739, that many moral arguments slip without warning from statements with "is" to conclusions with "ought", without explaining how that step is justified. P2 is exactly that step.
The word "natural" also changes meaning as convenient:
Sense of "natural" What it means Problem Statistical What most people do It's the appeal to popularity (D6): slavery was once the rule Evolutionary What our ancestors did Our ancestors also lived without anesthesia, writing or rights Biological What the body can do Being able isn't needing, nor ought (C3) Opposite of artificial What doesn't pass through human hands Industrial meat is one of the most artificial products there are - b
Where the argument breaks
1. Nature isn't a moral guide.
John Stuart Mill, in the essay Nature, published in 1874, put the problem clearly: if imitating nature were a standard of conduct, it would be right to kill, torture and destroy, because nature does so all the time. Either we accept that conclusion, or we admit that being natural was never, in itself, a reason to consider something good.
2. No one applies P2 consistently.
Infanticide, rape and violence between groups also appear in other species and in human history. No one concludes they're legitimate. In the other direction, almost everything we're proud of is unnatural: medicine, glasses, laws that protect the weak, the very idea of rights.
3. What is defended isn't natural.
Broiler chickens were bred to grow so fast that they're slaughtered at a few weeks old. Dairy cows are made pregnant again and again. None of this exists without technology, confinement and industry. The argument borrows the image of the ancestral hunter to defend a practice he wouldn't recognize.
4. Nature also teaches the opposite.
If the species' past defined what is legitimate, the plants our ancestors ate would count just as much, and so would cooperation, empathy and caring for the vulnerable, which are also part of our evolution. Choosing only the part that confirms the habit is convenient selection.
5. Today there's an alternative.
The argument ignores the change of context. For anyone with access to a varied diet, meat is no longer necessary: the US Academy of Nutrition and Dietetics considers well-planned vegan diets healthy and appropriate for all stages of life.
6. Research shows what the argument is for.
Piazza and colleagues found, in 2015, that "natural" is one of the four justifications most used for eating meat, along with normal, necessary and nice. Together they covered between 83% and 91% of the justifications participants gave, and those who most agreed with them felt less guilt and gave animals less moral consideration. The argument works less as a reason and more as relief.
- c
Data and sources
Source What it says Note Hume, A Treatise of Human Nature (1739), book III The move from "is" to "ought" needs justification Origin of what is called Hume's law Mill, Nature, in Three Essays on Religion (1874) Imitating nature would lead to approving killing, torture and destruction Also used in the book Veganismo Baseado em Evidências (in Portuguese) Piazza et al., 2015, *Appetite* Natural, normal, necessary and nice cover 83% to 91% of the justifications for eating meat Six studies; shows the psychological function of the argument Academy of Nutrition and Dietetics, 2016 Well-planned vegan diets are healthful, nutritionally adequate and appropriate for all stages of life Official position; includes the need for a reliable source of B12 - d
The strongest counter-reply: it's not nature, it's necessity and adaptation
The most serious version drops "natural is good" and says something more modest: we're omnivores, the human body is adapted to a varied diet, and asking people to give up something so rooted in biology and culture would be asking too much. Nature doesn't dictate morality, but it defines what is reasonable to expect of a human being.
- e
Why the counter-reply doesn't reach the conclusion
It changes the argument.
It stops being C1 and becomes about necessity (family G) and difficulty (family J). Both questions are empirical, and the answers are in those chapters.
Adaptation explains; it doesn't justify.
We're also adapted to aggression, favoring our own group and fearing strangers, and we expect people to control those.
What's reasonable to expect has changed.
Asking a hunter of the past to stop hunting would have been asking too much. Asking someone at the supermarket to choose beans instead of chicken isn't.
Difficulty doesn't change the harm.
Something being hard to give up may lessen the blame of those who haven't changed yet. It doesn't make what's done to the animals acceptable.
Reasoning errors
Logical
Is the form valid?
Appeal to nature
Hume's law (from is to ought)
Equivocation
Epistemological
Does the evidence support it?
Convenient selection
Anachronism
Moral
Is the criterion coherent?
Description instead of justification
Biases
The 4Ns rationalization
"Natural" is one of the most used justifications and is linked to less guilt
Naturalness bias
What is perceived as natural is judged better and safer
Rozin and colleagues, Appetite (2004): the preference for the natural has practical and moral motives
Meat paradox
The tension between liking animals and eating them is eased by ready-made justifications
Motivated reasoning
The "natural" criterion is used only when it confirms what one wants
General literature on motivated cognition
Extrapolations
The principle being tested is: "what is natural for the species is legitimate".
If it applied to…Violence between groupsTap to see
War and conquest would be legitimate, since they appear throughout human history
Contradicts international law itself
If it applied to…InfanticideTap to see
It would be acceptable, since it occurs in several species and in human societies
No one accepts this
If it applied to…MedicineTap to see
Vaccines, antibiotics and surgery would be suspect for not being natural
The argument is used by people who use them
If it applied to…Disease and disabilityTap to see
There would be no reason to treat them, since they're natural
Shows nature isn't a standard of good
Contradictions
Medicine, vaccines, glasses, surgery and the internet the argument is posted on.
No one defends infanticide or might makes right on the basis of nature (see C6).
Animals genetically selected, medicated, confined and slaughtered on an industrial scale.
Controlling impulses is seen as a sign of maturity, except when the impulse is eating meat.
No one lives like their ancestors in housing, medicine or transport, and only in food does the past become a rule.
What the argument gets right
What is true
There are truths here. Humans are omnivores and can digest meat, and eating animal foods played a role in our species' history. It's also true that habits rooted in biology and culture are hard to change, and that this deserves understanding, not contempt.
But
The mistake is treating that history as permission. Nature explains where we came from; it doesn't decide where we should go. The same species that hunted learned to care for those who can't defend themselves, and that is also part of our nature.
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:
- The Objection That Consuming Animals Is Natural Vol. IV, ch. 5
- If Speciesism Is Natural, Is Speciesism Justified? Vol. I, ch. 8
References
Philosophy
- A Treatise of Human Nature, book III, part I, section I.
- Nature. In Three Essays on Religion.