Does it matter that animals can’t consent?

The objection

“Consent is a human concept. Animals can’t give it or withhold it, so it makes no sense to say we’re violating it by using them. The whole framing is a category error.”

The answer

A pig can’t sign a form or agree to anything, so on the narrow point the objection is right. Consent is the way people who can speak for themselves protect their own interests, though, and when someone can’t give it, neither law nor medical ethics decides that anything may be done to them. The objection goes wrong at the next step, when it treats the absence of a yes as permission, something the law refuses to do for a newborn or a person in a coma.

What happens when a person can’t consent?

When a person can’t consent, others are bound to act in that person’s interests. The UN Convention on the Rights of the Child (1989) makes a child’s best interests “a primary consideration” in all actions concerning children, newborns included [1]. In England and Wales, the Mental Capacity Act 2005 requires anything done for a person who lacks capacity, which includes someone in a coma, to be done in their best interests [2]. The World Medical Association’s Declaration of Helsinki (2024) lets such people take part in medical research only under strict limits, normally with a legal representative’s agreement, and says that where they can still signal assent, their dissent should be respected [3]. Philosophers discuss the wider point under a name the Stanford Encyclopedia of Philosophy calls unfortunate, the problem of marginal cases: infants and people in comas lack the rational, self-reflective capacities often used to decide who counts morally, yet we treat them as counting (Gruen and Monsó, 2024) [4].

What does a pig’s behaviour at slaughter show?

A pig’s behaviour at slaughter can show fear. EFSA, the European Union’s food safety agency, suggests assessing fear in pigs at slaughter by high-pitched squealing, escape attempts, reluctance to move and turning back, which it defines as a pig facing the stunning area that turns round and tries to return to the holding pens (2020) [5]. Pigs squeal readily, EFSA notes, when they are scared, “forced to do something they do not want” or in pain, and it traces that fear and pain mainly to badly designed or maintained premises, rough handling and sudden loud noise [5]. The pig has an interest in avoiding that fear whether or not it can consent. In a 2015 paper on animal research, Kantin and Wendler argued that researchers have welfare-based reasons to consider, and in some cases respect, the dissent of every animal they use, and an additional, agency-based reason that applies at least to chimpanzees [6].

Can farmed animals be harmed?

Farmed animals can be harmed, and the capacity to be harmed, rather than the capacity to agree, is what the protections above exist for. Being unable to consent leaves a pig’s fear and pain intact and removes only the protection consent would give it, which in a newborn we would treat as a reason for more care. The New York Declaration on Animal Consciousness (2024) finds strong scientific support for conscious experience in mammals and birds, pigs, cattle and chickens among them, and at least a realistic possibility of it in all vertebrates, fish included, and in many invertebrates [7]. Where that possibility is realistic, the declaration says, it is irresponsible to ignore it in decisions affecting the animal [7]. The law does protect pigs at slaughter: a 2009 EU regulation, which the UK kept after Brexit, says animals “shall be spared any avoidable pain, distress or suffering during their killing and related operations” [8]. It governs how a pig is killed and does not ask whether being killed is in the pig’s interests, which is the question the law asks for the newborn and the coma patient.