The philosophical case against arbitrary species discrimination — and what it means in practice
Speciesism is the assignment of different moral worth or consideration to beings based on their species membership alone. It is the assumption that humans deserve greater moral consideration than other animals simply because they are human — not because of any specific morally relevant capacity they possess.
The term was coined by psychologist Richard Ryder in 1970 and popularised by philosopher Peter Singer in his 1975 book Animal Liberation. Singer drew an explicit analogy with racism and sexism: just as it is arbitrary and unjust to discount someone's interests because of their race or sex, it is arbitrary and unjust to discount someone's interests because of their species.
The antispeciesist argument has a simple structure:
This does not necessarily mean treating all animals identically to humans. It means that when comparing like interests — the interest in avoiding pain, for example — species membership should not determine whose pain counts more.
Peter Singer's utilitarian antispeciesism: we should maximise wellbeing and minimise suffering across all sentient beings. Species is morally irrelevant — what matters is the capacity to suffer and experience pleasure.
Tom Regan argued that all "subjects of a life" — beings with beliefs, desires, perception, memory, emotional life — have inherent value that cannot be traded off for aggregate benefit. This includes most mammals.
Standard contractarianism (Rawls) excludes animals as they can't participate in contracts. Modified versions extend justice to animals as beings who can be harmed and who cannot advocate for themselves.
Feminist care ethics emphasises relationships and responsibilities. Our relationships with animals — particularly domesticated ones — generate genuine caring obligations that speciesism ignores.
Martha Nussbaum extends her capabilities approach to animals: each sentient animal has a right to flourish according to its nature. Preventing animals from realising their central capabilities is an injustice.
Moral consideration should extend to all sentient beings. The foundation of moral status is sentience — the capacity for subjective experience — not species, intelligence, or social membership.
Response: Infants and some cognitively disabled humans also can't participate in moral reasoning. We don't exclude them from moral consideration. The capacity for reasoning may be relevant to moral agency (who can be held responsible) but not to moral patiency (who deserves consideration).
Response: This is correct, and antispeciesists agree. A fish doesn't have an interest in voting or reading novels. But fish do have an interest in avoiding pain and living out their lives. Antispeciesism says these interests should count, not that they're identical to human interests.
Response: That predation occurs in nature doesn't tell us what humans should do. Natural processes include earthquakes, cancer, and infant death — none of which we consider morally acceptable when we can prevent them. The fact that lions kill gazelles doesn't license us to kill animals unnecessarily.
Response: Antispeciesism doesn't require identical treatment of all life — it requires giving proportionate weight to interests based on morally relevant properties (like the capacity to suffer). Uncertainty about where to draw lines doesn't invalidate the clear cases at the core: mammals and birds demonstrably suffer and deserve serious moral consideration.
Speciesist thinking pervades current law and social practice in ways that are difficult to see from inside them:
Antispeciesist philosophers argue that future generations will look back on our treatment of animals the way we now look back at other historical moral catastrophes — with a mixture of horror and disbelief that it was ever considered normal.
Taking antispeciesism seriously has radical practical implications:
Antispeciesism Peter Singer Animal Liberation Tom Regan Moral Philosophy Animal Rights Sentience Ethics