Utilitarianism and animals

Utilitarianism was the first modern ethical theory to take non-human suffering seriously on its own terms, and it remains the dominant lens through which the contemporary animal movement counts costs and benefits. Its claim is simple: what matters morally is the experience of sentient beings, and more of it on the good side and less on the bad is the work of ethics.

Bentham’s footnote

In 1789 Jeremy Bentham published An Introduction to the Principles of Morals and Legislation. In a footnote to chapter XVII — addressing what beings fall within the protection of law — he made the observation which every subsequent animal ethicist has cited. The French, he wrote, had just begun to recognise that skin colour is no grounds for abandoning a person to the caprice of a tormentor. The day may come, he continued, when the rest of the animal creation acquires the rights which could never have been withheld from them but by the hand of tyranny. A full-grown horse or dog is beyond comparison a more rational, as well as a more conversable animal, than an infant of a day, a week, or even a month old.

Then the sentence which did the philosophical work:

The question is not, Can they reason? nor, Can they talk? but, Can they suffer? (Bentham, 1789)

Bentham’s move was to pull the criterion of moral status away from intellectual capacity and onto the capacity for experience. Once that substitution is made, the boundary of moral concern stops tracking species and starts tracking sentience.

Singer and equal consideration of interests

Animal Liberation (Singer, 1975; revised as Animal Liberation Now, 2023) took Bentham’s footnote and built the modern movement around it. Singer’s central principle is not that all animals are equal in capacity, nor that they have the same rights as humans, but that like interests deserve like consideration regardless of whose interests they are. A pig’s interest in avoiding severe pain is no less real, and no less weighty in the moral arithmetic, than a human’s interest in a comparable sensation.

From this principle Singer draws two conclusions. First, speciesism — the practice of assigning less weight to an interest simply because it belongs to a member of another species — is structurally analogous to racism and sexism: all three privilege a biological category over the morally relevant feature (Singer, 1975; cf. Ryder’s 1970 coinage). Second, industrial animal agriculture, which inflicts enormous suffering on beings capable of it in order to produce food for which adequate alternatives exist, cannot survive any honest utilitarian calculus. The conclusion is not a claim about rights; it is a claim about arithmetic.

Preference versus hedonic utilitarianism

Utilitarianism is not a single theory. Two variants matter most for animal ethics.

Hedonic utilitarianism, descending from Bentham and Mill, takes the goods to be maximised as pleasurable experiences and the bads as painful ones. On this view any being capable of pleasure and pain has a welfare that counts directly.

Preference utilitarianism, which Singer defended for several decades in Practical Ethics (Singer, 1979; 3rd ed. 2011), takes the goods to be the satisfaction of preferences — forward-looking desires about one’s own life. This variant generated what became known as the replaceability argument: if an animal has no preferences that extend beyond the present moment, then painlessly killing it and replacing it with an equally happy animal may not be a net harm. Singer deployed the argument cautiously, and only for beings he took to lack a conception of themselves as continuing through time; he argued that mammals and birds almost certainly do not qualify as replaceable in this sense. In the 2011 edition of Practical Ethics he moved partway back toward hedonic utilitarianism, conceding that the preference framework strained under reflection. Critics (Smart & Williams, 1973; later commentators) have used replaceability as a reductio against utilitarian theories of animal ethics, but the argument cuts less sharply once one notices that almost every farmed animal has interests in the next moment, the next meal, the next social interaction — interests that are cut short by slaughter.

Welfare capacity and the Rethink Priorities moral-weight work

If utilitarianism is arithmetic, the hard part is the numbers. How much does a chicken’s suffering weigh against a pig’s, or a shrimp’s against a salmon’s? Twentieth-century philosophers largely waved at this question. The Rethink Priorities Moral Weight Project (Fischer et al., 2022–2023) is the most ambitious attempt to answer it empirically. The project estimates welfare ranges — the plausible span between a species’ worst and best experiences — using behavioural, neurological, and evolutionary evidence, and then expresses them relative to a human baseline of one.

The headline finding is that under reasonable assumptions the expected welfare range of even distant species (shrimp, silkworms, black soldier flies) is not negligible, and the sheer numbers involved — hundreds of billions of shrimps, perhaps a trillion fish — mean that their aggregate welfare may dominate many cause-areas that appear human-centric. Adam Shriver’s work on the asymmetry between pleasure and pain as contributors to welfare (Shriver, 2014) underwrites one of the project’s methodological commitments: suffering has evolutionary priority over pleasure, which matters when you are estimating the welfare profiles of beings you cannot interview.

Whether one accepts Rethink Priorities’ exact numbers, the methodological move — that moral weight is empirically tractable rather than brutely stipulated — is the most important development in utilitarian animal ethics since Singer.

Effective altruism and contemporary animal welfare

The effective altruism community has absorbed this apparatus and built decision-making institutions around it. Animal Charity Evaluators, the Open Philanthropy Project’s Farm Animal Welfare programme, The Humane League, the Shrimp Welfare Project, and the Wild Animal Initiative all share a broadly utilitarian premise: the right intervention is the one that prevents the most suffering per dollar, and tractability can be studied. The corporate cage-free and broiler commitments of the late 2010s — hundreds of companies, billions of birds — were engineered under this frame.

Utilitarianism also opens a frontier most other ethical theories neglect: wild animal welfare. Faria and Paez (2019) argue that if suffering in nature matters morally in the same way as suffering in farms, then the scale of wild-animal suffering — predation, starvation, parasitism, climatic stress across trillions of vertebrates and quintillions of invertebrates — generates strong prima facie reasons to research interventions, from contraceptive management to disease treatment, even where the cultural instinct is to leave nature alone. The position is contested, but it is a genuine output of taking the calculus seriously.

Responses to common objections

The demandingness objection. If we must always act to maximise welfare, morality becomes impossibly demanding. Most utilitarians now accept a distinction between obligation and supererogation, or adopt satisficing or two-level variants (Hare) that leave room for ordinary lives.

The integrity objection. Bernard Williams famously charged utilitarianism with ignoring the agent’s own projects and attachments (Smart & Williams, 1973). Applied to animal ethics the objection lands more weakly, because the demand — stop eating sentient beings when adequate alternatives exist — is not an assault on anyone’s integrity. It is simply a change of diet.

Aggregation worries. Could enormous numbers of tiny pleasures swamp a real harm? Utilitarianism does permit aggregation, which is precisely why the 80-billion-land- animal figure (FAO, 2022) and the trillion-fish figure carry moral weight: the numbers are the point.

The replaceability objection. Addressed above: it trades on a preference- utilitarian premise most contemporary animal utilitarians, including the later Singer, have softened, and it misdescribes the forward-looking interests of actually-existing farmed animals.

Where the argument leaves us

The utilitarian case does not require a reader to accept that animals have rights, that they are subjects-of-a-life, or that they possess inherent dignity. It requires only that their suffering counts, and that when it is great and the cost of preventing it is small, the arithmetic points one way. Once the footnote is granted, the rest follows — not as a philosophical flourish, but as a standing invoice morality hands to anyone who thinks consistency matters.