Peter Singer Forgets Boethius

What makes human beings so special? As Catholics, we often take for granted that humans beings have a special status in the world because we are made in the image of God. As such, human beings are fundamentally different kinds of things from other animals. In recent years however, this position has been critiqued by certain prominent philosophers. Peter Singer, the prominent ethicist best known for his controversial views regarding the treatment of animals and related life issues such as abortion and euthanasia, is one such critic. Singer argues that classic attempts to distinguish between humans and other animals fail. He believes the source of being worthy of moral consideration is one’s ability to suffer, not some special quality unique to humanity. Below I will examine Singer’s arguments against sharply distinguishing humans and animals and show how he fails by overlooking an extremely important definition of the word “person” from Boethius. 

Singer’s Dichotomy

Singer argues that there are two possible ways to distinguish humans from animals: 1) an appeal to abilities that are morally relevant and unique to humans and 2) an appeal to our species. He argues that both of these alternatives fail.

In terms of human abilities, Singer of course grants that humans do have mental abilities that far transcend those of other animals even very intelligent chimpanzees. However, Singer points out that not all humans have these abilities. Infants and mentally disabled humans do not have mental abilities that go beyond even animals like chickens or cows. When discussing the right to life Singer states:

We may legitimately hold that there are some features of certain beings that make their lives more valuable than those of other beings, but there will surely be some nonhuman animals whose lives by any standards are more valuable than the lives of some humans. A chimpanzee, dog, or pig, for instance, will have a higher degree of self-awareness and a greater capacity for meaningful relations with others than a severely retarded infant or someone in a state of advanced senility.


Thus, if it is ethical to prefer human lives and interests over those of nonhuman animals because of our special mental abilities, then it would follow that we can also prefer some animals to comparatively unintelligent humans who lack such abilities. If e.g., it is legitimate to do experimentation on animals for scientific research, it would be equally legitimate to do such experimentation on infants or the mentally disabled. This is obviously an unwelcome conclusion that most people would reject. Thus, Singer reasons, this line of argument is a failure.

What does unite all human lives, from those of the unborn through the elderly, is that they are members of the species homo sapiens. Perhaps this unique feature is enough to ground our ethical preference for humans over and against animals. However, Singer argues that this view is worse than the prior alternative and indeed equivalent to racism. Just as the racist picks morally irrelevant qualities such as skin color and chooses to preference the interests of his own race, so too does the human choose arbitrary biological features and choose to preference human interests over and against those of nonhuman animals. Such a preference for species is called speciesism. As Singer states, “Racists violate the principle of equality by giving greater weight to the interests of members of their own race… Similarly, speciesists allow the interests of their own species to override the greater interests of members of other species. The pattern is identical in each case.”2

Singer recognizes that there are morally relevant differences between animals and humans but, as we saw, none sufficient to categorically separate the two. If animals can suffer, according to Singer, they have interests. If they have interests, these need to be considered along with our own. Singer then uses this underlying ability to suffer as a key to grounding animal protection in his philosophy. Singer’s view as to why suffering should form the basis for moral consideration is worth it’s own treatment. For our purposes here, I merely want to show that Singer has missed an important consideration, namely the classical definition of personhood. His above mentioned dichotomy is a false one.

Boethius’ Third Option

Singer has overlooked not only the true distinguishing factory between humans and animals but also one that is very prominent historically. When Singer speaks of persons, he uses John Locke’s definition of person which he quotes as “A thinking intelligent being that has reason and reflection and can consider itself as itself, the same thinking thing, in different times and places.”3 This definition, at face value, defines person on the basis of ability. An infant, presumably, would not be a person since an infant lacks the ability to reason, reflect on itself as itself. 

However, a much older definition of person, proposed by Boethius in the sixth century, is a better one. Boethius defined person as an individual substance of a rational nature. Boethius’ definition is similar to Locke’s in that both make reference to rationality. However, while for (Singer’s reading of) Locke, it is one’s ability to use reason that makes one a person, for Boethius, it is one’s membership in a rational kind that makes one a person. Thus, for Boethius, an infant or even an unborn child would be a person because they have the same nature as adult human beings, namely, a rational nature. Whether or not infants can at the present moment or at any future moment use their reason is irrelevant to whether or not they are persons. Personhood is the function of being a certain kind of thing, not of having certain abilities at the present time or even some future or past time. 

Why Prefer Boethius?

While the purpose of this article is merely to show that Singer has not engaged the classical tradition, it is worthwhile to briefly show that there is good reason to prefer Boethius’ definition of personhood over Locke’s or any definition which depends on a creature’s specific abilities to think, remember etc. Locke’s definition and those like it seem to exclude from personhood humans who most people would agree are persons e.g. people in comas, small children, the mentally disabled, and others. By contrast, Boethius’ definition would count them as persons since they are members of a rational kind, namely humanity. One might object that this Boethian definition is mere speciesism, simply reducing personhood to members of the species homo sapiens.

However, Boethius’ definition is not speciesist because his definition is entirely consistent with their being multiple kinds of persons. Most theists who follow Boethius think for example that angels are persons as well. Further, for all we know there may also be intelligent alien persons who are not human. If such aliens existed, they would be persons on this view and should be treated as such. Moreover, if Singer is correct in attributing personhood to some known nonhuman animals such as chimpanzees, there is nothing on the Boethian definition that would prohibit such a move. Whether chimps are truly rational is of course highly controversial. Nevertheless, if we were to assume for sake of argument that they were, we could do so comfortably given Boethius’ account of personhood. Thus, the Boethian definition, while truly distinct from Singer’s proposed view, is not speciesist but rather a much more consistent way of applying the label of personhood.

The Implications of Personhood

With this classic definition in place, it becomes clear that Singer has not given a convincing argument for the consideration he thinks is due to nonhuman animals. The difference between being a rational thing and not being a rational thing is extremely significant, even more significant than the difference between the difference between being an animal vs. being a plant. Such a difference then cannot be glossed over in an ethical theory. Singer can disagree with Boethius, but he must show why Boethius is wrong. If we accept Boethius’ defintion, we can see some of the potential implications that have been worked out in the classic philosophical and theological tradition.

Thomas Aquinas for instance, says that rational creatures excel non-rational both by having a superior nature, and by having a more perfect end, i.e. coming to know God. Creatures, since they lack by nature the capacities of rational creatures of free will and knowledge of abstract things, cannot attain the same end as rational creatures. Since they themselves cannot attain that end, they are directed to it as means for man to do so. As Aquinas puts it, “God cares for all things for the sake of intellectual substances.”4

Singer is aware of such claims by Aquinas but dismisses them as merely religious claims when in fact Aquinas is arguing directly from the nature of personhood found in Boethius. In this section of the Summa Contra Gentiles, Aquinas gives seven arguments for this conclusion most of whose premises have nothing to do with God but rely merely on the distinction between a rational being and a non rational thing.

Beyond reason, we also know by revelation that our rationality is in fact something which images God himself. As Aquinas says,

While in all creatures there is some kind of likeness to God, in the rational creature alone we find a likeness of “image”… Now the intellect or mind is that whereby the rational creature excels other creatures; wherefore this image of God is not found even in the rational creature except in the mind


In addition to this passage from Genesis 1, we are told that God values human life so much that he chose to become a human in order to save human beings and unite them to himself. Thus, the value which each human life possesses is, as a recent decree from the Dicastery of the Doctrine and the Faith says, infinite. Revelation then fills in the picture that is vaguely sketched by reason and offers a foundation for our ethical focus on the life and dignity of the human person. 


We have looked at a false dichotomy offered by the atheist philosopher Peter Singer which attempts to undermine the special status human beings have in moral thought. As we saw, Singer simply skips over the classic definition of personhood offered by Boethius and offers a false dichotomy: either we prefer humans based on their abilities which entails unequal treatment of humans and even preference for animals over immature or disabled humans or we arbitrarily prefer humans and commit to speciesism, simply a more general form of racism or any other kind of bigotry our society has fought so long to eradicate. In contrast, if we use Boethius’ definition, we can see that humans are not persons simply because they are a certain biological species, but because they are individual substances partaking in a rational nature. This third option, falsifies Singer’s dichotomy and points toward the more full revelation of human dignity found in divine revelation. Being grounded in both reason and revelation, we can see the true value of human beings and apply this to our ethical theories and practices.

  1. Singer, Peter. Writings on an Ethical Life. Harper Collins, 2000, p. 44. ↩︎
  2. Ibid. 35 ↩︎
  3. Ibid. 76 ↩︎
  4. Aquinas, Thomas. Summa Contra Gentiles. Book III, Chapter 112. ↩︎
  5. Aquinas, Thomas. Summa Theologiae. Prima Pars, Question 93, Article 6. ↩︎

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