Home / A. Sentience and moral status / Part DIR
"Animals aren't conscious and don't feel pain like we do."
the claim that animals aren't conscious isn't a neutral position in the face of the evidence: it contradicts the current scientific consensus. And the milder version, "they don't feel like we do", changes the subject: difference isn't absence, and in some respects their experience may be worse, because they don't understand what's happening and can't be reassured.
Short answer
This isn't an open question. In 2012, a group of neuroscientists signed the Cambridge Declaration stating that lacking a neocortex doesn't stop an animal from having affective experiences, and in 2024 the New York Declaration, signed by hundreds of researchers, went in the same direction. Saying "they don't feel like us" doesn't help either: different isn't less. A pig in the slaughterhouse doesn't understand what's happening and can't be reassured, which may make the experience worse, not better.
For children
When you accidentally step on a dog's tail, it yelps, moves away and is then afraid to come close. That isn't just the body moving by itself: it felt it, remembered it and became afraid. Scientists have studied this a lot, and today most agree that animals feel pain, fear and joy. It may be a little different from how we feel, but it hurts all the same.
"If they don't feel, why does the pharmaceutical industry test painkillers on them?"
Como pode aparecer
"It's just reflex, like when the doctor taps your knee."
"Animal pain is different; they forget."
"They have no idea what's happening, so they don't suffer."
"Chickens don't even have the brains for that."
"Fish don't have a neocortex, so they don't feel pain."
"Do you really think a cow suffers the way a person does?"
"Nociception isn't pain; without the right cortical structures, there's no conscious experience."
"Descartes already said it: they're automata."
"They feel, but not like us." (uses the difference to reduce the weight, without saying by how much)
The strongest version
"Animals don't feel like we do; it's just reflex."
Strongest version (steelman). The serious version isn't Cartesian; it's neuroscientific. It was defended, for example, by Brian Key (2016) regarding fish:
- P1Conscious pain, unlike nociception, depends on specific brain structures, such as the neocortex and its connections.
- P2Many animals lack those structures.
- C1So these animals can react to harmful stimuli without any conscious experience of pain.
- P3There's only moral harm when there's conscious experience.
- C2So using them causes no moral harm.
The distinction between nociception (detecting a harmful stimulus, which can be automatic) and pain (the unpleasant experience) is legitimate and important. The argument errs in assuming the first happens without the second in every species without a neocortex.
There's also the mild version, more common in conversation: "they do feel, but not like us". This version doesn't deny sentience; it uses the difference to reduce the moral weight of suffering, without saying by how much or why.
The argument is valid. Its soundness fails at P1, which confuses a specific structure with the function it performs, and at P2, which ignores analogous structures in other animal groups.
Full answer
- a
Reconstruction and diagnosis
The argument has two very different versions, and they shouldn't be mixed up.
Version What it claims How it's assessed Strong (Cartesian or neuroanatomical) There's no conscious experience, only nociception It's an empirical claim, and current evidence goes against it Mild They feel, but differently and less intensely May be partly true, but doesn't authorize the conclusion; difference isn't absence The strong version makes a known mistake in comparative neuroscience: confusing structure with function. Requiring a neocortex for experience is like requiring bat wings for an animal to fly. Birds and octopuses, for example, solve complex problems with brain architectures very different from ours.
- b
Where the argument breaks
1. The scientific consensus is the opposite.
The Cambridge Declaration (2012) states that "the absence of a neocortex does not appear to preclude an organism from experiencing affective states" and that non-human animals, "including all mammals and birds, and many other creatures, including octopuses", possess the neurological substrates that generate consciousness. The New York Declaration (2024) reaffirms the point and extends it: there's strong support for mammals and birds, and a "realistic possibility" of conscious experience in all vertebrates and many invertebrates.
2. Science doesn't rely on a single anatomical criterion.
Pain assessment uses converging criteria: presence of nociceptors, opioid systems, behavior change after injury, learning to avoid what hurts, willingness to pay costs to avoid pain, the effect of painkillers on behavior (Sneddon et al., 2014). Fish, birds, mammals, octopuses and crabs pass several of these criteria.
3. Tests of emotional state are already routine in research.
The judgment bias test, created by Harding, Paul and Mendl (2004), showed that rats in worse conditions interpret ambiguous signals more "pessimistically", as humans do in negative moods. The technique was later applied to many species. This isn't activist intuition: it's methodology published in top journals.
4. The law has already followed the evidence.
A review of more than 300 studies, commissioned from Jonathan Birch's group (2021), concluded that cephalopods and decapods should be treated as sentient. The United Kingdom changed its law to recognize octopuses, lobsters and crabs as sentient beings.
5. "Not like us" can mean worse.
An animal that doesn't understand what's happening can't prepare, can't be reassured, doesn't know the pain will pass and can't ask for help. In humans, the inability to understand and anticipate usually increases suffering, not reduces it. So the cognitive difference doesn't justify discounting the weight of suffering; in many cases it justifies increasing it.
- c
Data and sources
Finding Source Reliability "The absence of a neocortex does not appear to preclude an organism from experiencing affective states"; mammals, birds and octopuses possess the neurological substrates of consciousness Cambridge Declaration on Consciousness, 7 Jul. 2012 High as a synthesis of experts Strong support for conscious experience in mammals and birds; a realistic possibility in all vertebrates and in cephalopods, decapods and insects New York Declaration, 19 Apr. 2024 High as a synthesis of experts A review of more than 300 studies concludes that cephalopods and decapods should be treated as sentient; the basis for the change in British law Birch, Burn, Schnell, Browning and Crump, 2021 (LSE) High (a systematic review commissioned by government) Rats in worse conditions interpret ambiguous signals more pessimistically, like humans in a negative mood Harding, Paul and Mendl, 2004, *Nature* High; method replicated in many species Converging criteria for assessing animal pain Sneddon et al., 2014 High (reference review) The position that fish don't feel pain Key, 2016, *Animal Sentience* A minority view: the article drew more than 30 published commentaries, most disagreeing, several pointing out that lacking a neocortex doesn't imply absence of pain - d
The strongest counter-reply: the hard problem of consciousness
The honest reply isn't "animals are machines", but: no one can explain why subjective experience exists, nor measure consciousness directly. Any behavior could, in principle, occur without anyone feeling. So attributing suffering to animals would be an inference by analogy, weaker the more distant the species. This is a legitimate philosophical concern, and the book doesn't pretend it doesn't exist.
- e
Why the counter-reply doesn't reach the conclusion
The same doubt applies to other humans.
There's no direct measure of consciousness in anyone. If uncertainty were enough to ignore suffering, the same would hold for anyone who isn't me.
Uncertainty isn't absence.
"We aren't sure" doesn't imply "they don't feel". It implies we must decide under uncertainty, which is different.
Under uncertainty, the cost of error decides.
Treating as sentient an animal that may not feel costs a different meal. Treating as insensible an animal that feels costs real suffering, multiplied by tens of billions of individuals a year. The New York Declaration states the same principle: when there's a realistic possibility of conscious experience, it's irresponsible to ignore it.
The analogy isn't weak for farmed vertebrates.
Pigs, cows, chickens and fish have nociceptors, opioid systems, physiological stress responses and avoidance behavior. The evolutionary distance is large for an insect, not for a mammal raised for food.
The skeptic already acts as if they knew.
Those who doubt animal pain accept anesthesia for their own dog before surgery, and accept that painkillers are tested on animals before reaching pharmacies.
Reasoning errors
Logical
Is the form valid?
Confusing structure and function
Non sequitur
False dichotomy
Epistemological
Does the evidence support it?
Contradicting the consensus
Cherry picking
Selective skepticism
Ignoring the asymmetry of risk
Moral
Is the criterion coherent?
Discount without criterion
Inverting vulnerability
Biases
Motivated denial of mind
Knowing an animal will be eaten reduces the mind we attribute to it
Bastian et al., 2012; replicated by Jacobs et al., 2024
Categorization as food
Classifying an animal as food reduces the perception that it suffers
Motivated skepticism
Much stronger evidence is demanded for the uncomfortable conclusion
Ditto and Lopez, 1992
Anthropodenial
Fear of seeming naive leads to denying obvious similarities, the mirror error of anthropomorphizing
Frans de Waal
Distance and invisibility
The suffering happens far away, with no sound or image for the consumer
The empirical basis of argument E7 ("I don't want to see")
Status quo bias
Accepting sentience would require changing habits, so the doubt is kept
General literature on motivated cognition
Extrapolations
The principle being tested is: "whoever lacks the brain structures we have, or doesn't feel like us, can be disregarded".
If it applied to…NewbornsTap to see
Their pain could be ignored. A baby's cortex is still immature, and they neither report nor understand their own pain; by the criterion, there'd be no experience to protect
This belief underpinned surgery on babies with minimal anesthesia until the 1980s (Anand and Hickey, 1987)
If it applied to…People with severe cortical lesionsTap to see
They'd lose protection from pain. If experience depends exclusively on the cortex, patients with extensive cortical damage wouldn't suffer
Medicine treats these patients' pain, and there's evidence that subcortical structures are enough for basic affective states
If it applied to…Other people in generalTap to see
Anyone could be treated as an automaton. There's no direct access to anyone's mind; other people's pain is always an inference
This is the old problem of other minds, and no one applies it to their own family
If it applied to…Beings with different biologyTap to see
An extraterrestrial life form without neurons like ours could be tortured even if it showed every sign of suffering
Shows that the relevant criterion is functional evidence of experience, not anatomical similarity
If it applied to…The arguer's own dogTap to see
Running it over or operating without anesthesia would be a matter of indifference. If animal pain is just reflex, that holds for all animals, not just the ones on the plate
Almost no one accepts this consequence, which shows the doubt is selective
Contradictions
Those who say animals don't feel pay for anesthesia to neuter their dog and for painkillers after surgery.
Human painkillers and anesthetics are tested on animals because their pain is assumed to work much like ours.
The same person says the dog "got jealous", "is happy" or "missed us", and denies similar states to the pig.
Punishing someone who beats an animal only makes sense if the animal suffers.
Doubt about sentience rarely reaches dogs and cats.
What the argument gets right
What is true
The distinction between nociception and pain is real and important: not every reaction to a harmful stimulus involves conscious experience, and a plant closing its leaves isn't suffering. Caution against projecting human feelings onto anything that moves is also healthy. And there are real differences between species: a fish's experience is probably not the same as a pig's, nor a pig's the same as ours. About more distant invertebrates, such as insects, scientific uncertainty is still large, and the book doesn't pretend otherwise.
But
The mistake lies in turning difference into absence and uncertainty into license. The moral question isn't whether the animal feels exactly as we do, but whether there's someone there for whom it is bad. For the animals we raise and kill in the greatest numbers, the evidence that there is someone is strong.
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:
- What Is Sentience and Why Does It Matter? Vol. II, ch. 3
- Which Beings Are Sentient? Vol. II, ch. 4
References
Provisional author-date format. The links indicate the sources checked in writing this chapter.
Declarations and reviews
- *The Cambridge Declaration on Consciousness* (2012).
- *The New York Declaration on Animal Consciousness* (2024).
- *Review of the Evidence of Sentience in Cephalopod Molluscs and Decapod Crustaceans*. LSE.
- Defining and assessing animal pain. *Animal Behaviour*, 97.
Studies and debate
- Cognitive bias and affective state. *Nature*, 427.
- Why fish do not feel pain. *Animal Sentience*, 3(1), and the replies published in the same volume.
- Pain and its effects in the human neonate and fetus. New England Journal of Medicine, 317.
Psychology
- Don't mind meat? Personality and Social Psychology Bulletin, 38(2); replication: Jacobs, T. P. et al. (2024).
- The effect of categorization as food on the perceived moral standing of animals. *Appetite*, 57(1).
- Motivated skepticism. Journal of Personality and Social Psychology, 63(4).
- Anthropomorphism and anthropodenial. Philosophical Topics, 27(1).
Philosophy
- Facing up to the problem of consciousness. Journal of Consciousness Studies, 2(3).
- Discourse on Method, part V.