Home / E. Relativism, freedom and evasions / Part DIR
"Veganism is opinion, not science."
no moral position is "just science", including the position of eating meat. Science answers questions of fact, such as whether animals feel pain, and its answers support veganism: there is broad scientific support for vertebrate sentience and growing evidence for many invertebrates. Ethics answers questions of value, such as whether it's right to cause that pain without need. Both have methods, and neither is "just opinion".
Short answer
Science doesn't say what's right, and it doesn't say so about any moral position, including eating meat. But it answers the factual questions that matter: do animals feel pain? Yes, and in 2024 scientists from several fields signed a declaration recognizing strong support for consciousness in mammals and birds. The moral question is whether it's right to cause that pain without need. That's ethics, which isn't science, but isn't "just opinion" either.
For children
Science can find out whether a pig feels pain, and it already has: it does. But the question "is it right to hurt someone who feels pain?" is a different question. For that one, we use reason and ethics, which have their own rules too. And almost everyone agrees that hurting without need is wrong.
"If everything that isn't science is just opinion, is saying slavery was wrong also just opinion?"
Como pode aparecer
"That's ideology, not fact."
"Science doesn't say eating meat is wrong."
"That's just your opinion."
"Show me the study that proves meat is immoral."
"Value judgments can't be verified empirically."
"Morality is relative." (which is E2)
The strongest version
"That's ideology, not fact. Science doesn't say eating meat is wrong."
Strongest version (steelman):
- P1Science describes facts; it doesn't tell us what we ought to do.
- P2Veganism is a claim about what we ought to do.
- P3What isn't science is just opinion.
- CSo veganism is just opinion.
P1 and P2 are true: science alone doesn't produce moral norms. The problem lies in P3: if what isn't science is just opinion, then it's also just opinion that eating meat is acceptable, that stealing is wrong and that slavery was unjust.
The argument is valid. Its soundness fails at P3, and the conclusion applies equally against the arguer's own position.
Full answer
- a
Reconstruction and diagnosis
The debate about eating animals involves two kinds of questions:
Question Type What the answer says Do animals feel pain? Fact: science Yes, with strong support for mammals and birds and evidence for many others Is it possible to live well without eating animals? Fact: science Yes, according to the main nutrition bodies Is it right to cause suffering without need? Value: ethics Almost every ethical theory says no Veganism combines the scientific answers with a widely accepted moral principle.
- b
Where the argument breaks
1. It cuts both ways.
If ethics is just opinion, the claim that eating meat is acceptable is too. The argument favors no one.
2. Ethics has methods.
Consistency, generalization, analysis of arguments and testing principles against similar cases are methods of moral philosophy. They make it possible to tell better positions from worse ones.
3. The relevant facts are scientific.
The New York Declaration on Animal Consciousness (2024) states there is strong scientific support for attributing conscious experience to mammals and birds, and a realistic possibility for all vertebrates and many invertebrates.
4. Almost everyone accepts the moral premise.
"Causing unnecessary suffering is wrong" is accepted by almost all people and theories. Veganism just applies that principle consistently.
5. Asking for "the study" confuses categories.
There's no study proving slavery was immoral, and no one concludes that this is just opinion.
- c
Data and sources
Source What it says Note The New York Declaration on Animal Consciousness (2024) Strong scientific support for consciousness in mammals and birds; a realistic possibility in all vertebrates and many invertebrates Signed by hundreds of researchers Academy of Nutrition and Dietetics, 2016 Well-planned vegan diets are appropriate at all stages of life Answers the factual question about need - d
The strongest counter-reply: science doesn't say how much animals weigh
The most serious version grants the facts, but says science doesn't tell us how much animal suffering weighs against human interests, and that this weighing is subjective.
- e
Why the counter-reply doesn't reach the conclusion
The weighing doesn't need to be exact.
It's enough to see that the pleasure of a flavor weighs less than an animal's life and suffering.
Moral weighing isn't arbitrary.
We use criteria such as severity of harm, necessity and alternatives, as in any other moral issue.
The difficulty doesn't favor the status quo.
If we don't know the exact weight, that's a reason for caution, not for continuing to cause the harm.
Reasoning errors
Logical
Is the form valid?
False dilemma
Selective application
Epistemological
Does the evidence support it?
Scientism
Category confusion
Biases
Motivated reasoning
Skepticism shows up only when it protects the habit
General literature on motivated cognition
Naive realism and the bias blind spot
One's own position seems factual; the other's, emotional
Extrapolations
The principle being tested is: "what isn't science is just opinion".
If it applied to…Human rightsTap to see
They'd be opinion, since they aren't scientific facts
No one accepts this
If it applied to…Condemning racismTap to see
It would be opinion
No one accepts this
If it applied to…The claim that eating meat is acceptableTap to see
It would also be just opinion
The argument turns against whoever uses it
Contradictions
And doesn't consider them "just opinion".
No one asks for "the study" to condemn mistreating a dog.
Which would be impossible if everything were just opinion.
What the argument gets right
What is true
The distinction between facts and values is real and important. Science doesn't settle moral questions on its own, and it's healthy to distrust anyone who presents opinions as if they were data. It's also true that there are scientific uncertainties about the sentience of some animals.
But
But ethics isn't no man's land. It has methods, and what it asks here is little: to apply to animals that science recognizes as sentient a principle almost everyone already accepts.
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:
- Attempts to Justify Speciesism That Appeal to Metaethics Vol. I, ch. 15