Practical Ethics

Written by Joseph Moore

This year, Peter Singer published Animal Liberation Now, a significantly updated version of his 1975 animal rights classic. Both the original and revised text argue that humans should refrain from inflicting unnecessary suffering on non-human animals, especially the cruel practices still commonly employed in factory farming and animal experimentation. And as a step towards this collective action, Singer urges his readers to modify their individual purchasing practices by preferring cruelty-free products or, even better, committing to vegetarianism or veganism.

The bulk of the revisions in the new edition concern the empirical facts on the ground, both the positive changes in the treatment of non-human animals since the original printing as well as ongoing, legally sanctioned cruel practices. Unfortunately, the philosophically weakest part of Singer’s influential argument, which occurs in the first chapter, has received no additional support in this edition. This is his claim that ‘the capacity for suffering and enjoyment is a prerequisite for having interests, a condition that must be satisfied before we can properly speak of interests at all’. The supposed necessity of sentience for having interests is why Singer limits his ‘principle of equal consideration of interests’ to (some) animals and does not extend it to living things in other kingdoms—plants, fungi, bacteria, etc.—or other kinds of subjects. But this relatively undefended assertion was dubious in 1975 and is even more dubious now. Singer’s restriction of interests to sentient beings is just as arbitrary as the speciesism he decries.

What Singer calls ‘interests’ are now more commonly described as contributors to well-being or welfare or prudential value. By any name, the concept is that of what is (non-instrumentally) good for or beneficial to a given subject, i.e., what makes that subject better off. (To avoid begging questions, understand ‘subject’ in a syntactical sense, like the subject of a sentence, rather than a psychological sense involving conscious ‘subjectivity’.) There is now a rather large philosophical literature on well-being and the necessary and sufficient conditions for contributors to well-being. Singer’s hedonism, the view that only pleasure is fundamentally good for subjects and only pain fundamentally bad, is just one theory of well-being among many others.

At least one other theory of goodness-for-a-subject is almost as old and just as influential. According to Aristotle’s naturalist perfectionism, it is good for every kind of living thing (as well as for at least some collectives, such as human city-states) to fulfil its natural function based upon its distinctive capacities. Derivatively, it is also good for every kind of living thing to have internal states (e.g., bodily integrity) and external resources (e.g., sources of nutrition) that enable it to perform its natural function well. And, in fact, Aristotle’s general biological theory explains how we know that all living things have their own forms of well-being. Aristotle claims that it is distinctive of all living things—plants, fungi, animals and, if he were aware of them, single-celled organisms—to have capacities and needs for nutrition, growth, self-maintenance and reproduction. Further, it is distinctive of all animals to have capacities for sensation, perception and locomotion and to have corresponding sensory, desiderative, emotional and social needs. While what is distinctive of humans is (supposedly) our rationality, we still share in all of these common animal and ‘vegetative’ needs. We already accept that it is good for humans to meet these needs, to survive and reproduce and avoid serious pain and engage in social relationships. Well, it is just as good for other animals and other living things to meet these same, common needs. And notice how this is just like Singer’s argument that non-human animal pain matters morally: we know human pain matters and non-human animals can experience the same kind of pain, so theirs matters just as much.

Now, Aristotle’s views on the subject are important and influential enough in the history of philosophy that his theory of goodness or ‘interests’ should not have been dismissed without comment by a philosopher in 1975. But the philosophy and ‘positive’ psychology of well-being has exploded in the intervening decades. There are now many more views under discussion, and relatively few expert participants in these discussions nowadays are hedonists. There are plenty of other purely psychological views, as well as more ‘objective’ (not-purely-psychological) views. If we accepted any of these alternatives, we would thereby draw the line of interests and moral concern in different places from Singer’s line of sentience (i.e., capacity for pleasure and pain). On a perfectionist view like Aristotle’s, more living things than just sentient animals would have interests; on a more cognitively complex view from positive psychology (involving, e.g., a sense of meaning or purpose), only some but not all sentient animals would have interests. Here in 2023, Singer should not rest his book’s entire argument on a widely rejected assumption with no more defense than that Bentham held the view.

To be fair, rejecting Singer’s hedonistic premise does not undermine his practical moral conclusions. We can charitably revise his argument to ignore the claim that pleasure and avoidance of pain are the only morally relevant interests and instead assert that pleasure and pain avoidance at least are morally relevant interests. We already accept that we ought not inflict needless suffering on humans, non-human animals are also capable of suffering and so, on pain of arbitrariness, we ought not inflict needless suffering on non-human animals. Combined with all the factual reporting about conditions in factory farms and labs, this is a convincing enough argument that we, collectively, ought to stop such unnecessarily cruel practices.

The remaining philosophical problem for Singer, however, is that it is, pre-theoretically, very plausible that pleasure and pain avoidance do not exhaust well-being and interests. Indeed, to anyone not already in the grips of a psychologistic theory of well-being, it should be intuitive that things can be good or bad, better or worse for any kind of living thing and not just the relatively small number of those with mental states. It is straightforwardly good for a typical plant to have access to sunlight, water and soil nutrients. It is bad for a typical mushroom to be placed in a bright, hot, dry environment. It is good for a methanotrophic bacterium to have access to methane, bad for a typical bacterium to be bathed in pure alcohol. These non-animals have ‘interests’, in the sense of goodness-for-a-subject, even if they do not consciously ‘take an interest’ in them.

As a result, Singer has not given us a principled reason for caring about the interests of all animals but not other types of subjects with interests. He briefly considers the possibility that plants have interests of moral concern but still thinks it will depend entirely upon plants’ ability to feel pain. But plants and other living things do intuitively have interests independently of feeling pain, and this problematises Singer’s position. For he places great emphasis upon the idea that all species’ interests are equally deserving of moral consideration and that accepting anything less would constitute objectionable speciesism. But he is guilty of the same kind of arbitrariness by restricting ‘interests’ to sentient animals. Given a more plausible and inclusive theory of well-being, Singer’s argument commits him to the equal moral relevance of the interests of non-animal beings.

In this light, the ‘What about plants?’ objection that Singer dismisses takes on much greater force. It would require a great shift in our moral beliefs and our practices to treat the interests of plants, fungi and single-celled organisms as equally worthy of moral consideration as humans and other animals—a far greater shift than merely to give non-human animals equal consideration. If we wish to avoid the implication that chopping down a healthy tree is morally tantamount to a gruesome murder, we will need to provide some moral justification for privileging the interests of some kinds of living things, perhaps the interests of sentient animals over non-animals. It seems reasonable to look for some such justification.

But it is not clear that Singer, in particular, could accept this. In the first place, any such pattern of justification could turn out also to justify privileging humans over non-human animals, threatening his moral conclusions. But moreover, it is precisely this kind of privileging of interests that Singer denounces with comparisons to sexism, racism, etc. We could easily charge Singer’s animal-privileging position with ‘kingdomism’, which is just another form of ‘speciesism’. At the very least, Singer owes some principled explanation for drawing the line of moral consideration at sentience, as he clearly would like to. This could involve a sophisticated defense of hedonism about well-being against the objections that have been raised to it and the many alternatives on offer. Without any such argument or explanation in this text, however, Singer’s ‘zoocentric’ position appears to be one of the more arbitrary positions one could take here. It would be less arbitrary either to treat all living things’ interests equally (as counterintuitive as that might be) or to unabashedly privilege interests on some basis (perhaps in proportion to the similarity of other creatures’ complete interests to our own). Neither approach would be likely to vindicate animal cruelty, and so Singer may rest content to have preserved his main conclusion: the need for animal liberation. But a more consistent position might lend nuance to our more concrete interpretations of this goal or of our other moral obligations.