Are Humans and Animals Moral Equals?
A Sentience Article from

FROM Robert C. Jones
October 2021

Given that rats and pigs and boys are sentient, rats and pigs and boys all have robust interests; to avoid speciesism, in considering these interests, we must do so equally.

In a 1985 interview, PETA President Ingrid Newkirk uttered a provocative (and, notorious (depending on your point of view)) remark:

“Animal liberationists do not separate out the human animal, so there is no rational basis for saying that a human being has special rights. A rat is a pig is a dog is a boy. They’re all mammals.”

Since then, the statement, “A rat is a pig is a dog is a boy”, has been used by anti-animal liberationists as a kind of reductio ad absurdum against the theoretical underpinnings of animal liberation. But most critics of Newkirk’s assertion seem to read the phrase as uncharitably as possible. Could she really intend that a rat and a human child are moral equals? Perhaps, but I think the answer requires a bit of nuance and an understanding of the work of Peter Singer.

All animals are equal

In his influential 1986 essay, “All Animals are Equal“, philosopher Peter Singer outlines the philosophical underpinnings of the kind of sentiment expressed by Newkirk. When we reflect, for example, on human social justice movements, we notice that one thing that underlies and connects these movements is a belief that, in an important and profound sense, all humans are equal. This belief, the principle of equality, is the key to making sense of Newkirk’s statement. But what does it really mean to say that all humans are equal? Given that humans differ from each other so significantly in their physical, moral, emotional, and cognitive abilities and capacities, surely, as a descriptive empirical assertion, claims of human equality in this sense are clearly factually untrue. But the principle of equality is not intended as a fully factual but rather as a normative concept. In this sense, equality is not a description but rather a prescription of how we should treat human beings. The primary empirical claim grounding the principle of equality is the fact that human beings are experiential subjects; that is, there is a “what-it’s-like” to be human, experiences philosophers refer to as qualia. Put in simpler terms, human beings are sentient.

Equal Consideration of Interests

This principle of equality, coupled with sentience, and combined with the interests that the possession of sentience provide (e.g., an interest in not being harmed), lead to the central principle driving Singer’s view: the principle of equal consideration of interests, the essence of which is to “give equal weight in our moral deliberations to the like interests of all those affected by our actions” (Singer, 2002, p. 8). When engaged in any decision-making procedure concerning how we ought to treat one another morally, this principle requires that we consider the interests of all humans equally. But since sentience provides the basis for the equality of human beings, and since human beings are not the only sentient beings, to be consistent, we must extend the principle of equal consideration of interests to all sentient beings. The principle of equal consideration of interests requires that we weight interests not on the basis of species (or race or gender), but on an individual’s abilities and capacities. To do otherwise, to privilege the interests of humans over nonhumans solely in virtue of species membership, is speciesist, plain and simple.

Yet, equality for nonhuman animals does not entail equality of treatment, but merely the equal consideration of interests. Adjudicating differences in treatment between competing interests requires what Singer calls the relevance principle. According to the relevance principle, whether a difference between individuals justifies a difference in treatment depends on the kind of treatment in question. Thus, equality for animals does not require, for example, that we grant pigs the right to vote, not because the interests of pigs are of less moral concern, but rather because pigs, unlike humans, have no interest in voting. On the other hand, since pigs, like humans, have an interest in not suffering, livestock production techniques that inflict suffering on pigs solely to satisfy the palates of consumers are impermissible. (Cochrane, 2012).

A rat is a pig is a dog is a boy?

In light of this discussion, we are better positioned to make sense of Newkirk’s claim. Given that rats and pigs and boys are sentient, rats and pigs and boys all have robust interests; to avoid speciesism, in considering these interests, we must do so equally.

Further reading

  • Cochrane, A., (2012). Animal Rights Without Liberation: Applied Ethics and Human Obligations, New York, NY: Columbia University Press.
  • Gruen, L. (2011). Ethics and Animals: An Introduction, Cambridge University Press.
  • Jones, R.C. (November, 2015). “Animal Rights is a Social Justice Issue“, Contemporary Justice Review, pp. 467-482.
  • Jones, R.C. (2013). “Science, Sentience, and Animal Welfare“, Biology and Philosophy, 28(1), 1–30.
  • McCabe, K. (August, 1985). “Who Will Live, Who Will Die,” The Washingtonian.
  • Proctor, H.S. (2012). “Animal Sentience: Where Are We and Where Are We Heading?”, Animals 2, 628–639.
  • Singer, P. (1986). “All animals are Equal”, in P. Singer (Ed.), Applied Ethics (pp. 226–228), Oxford: Oxford University Press.

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