Fellow Creatures is an outstanding philosophical work that achieves many things at once. Christine M. Korsgaard here provides an extended, nuanced and sophisticated response to a persistent question about Kantian moral theory: how can the view deal with creatures who are not rational beings in Kant’s sense, yet seem to have moral standing of their own? She also develops a theory of the good – and, relatedly, of the better – that advances her Kantian constructivist project. The book raises important questions about aggregation in ethics. It includes illuminating discussion of pleasure and its role, or lack thereof, in practical thought. And it ends with insightful and clear-eyed treatment of specific practical questions about human interactions with animals, including issues concerning farming, animal experimentation and the keeping of pets. Perhaps most importantly, Fellow Creatures displays and defends a moral sensibility in which the other animals figure as the individual centres of consciousness that they are, and a call to face the moral enormity of this truth.

Korsgaard begins with consideration of the claim that we human beings are somehow more valuable than the other animals. Rather than merely rejecting this claim, she argues that it barely rises to the level of falsehood. By her lights, it makes almost no sense at all. Section I makes the case for this startling position, laying out a theory of value along the way. On Korsgaard’s view, value is always tied to the perspective of some valuing creature: to be good is to be good-for such a creature, valuable from her point of view. Value thus comes into the world with creatures who have the relevant sort of perspective, valenced or teleologically organized perceptions of their environment. As a conceptual matter these are the animals. To be an animal is to experience the world as organized around your interests or functional good, not in the sense that it is necessarily hospitable, but in the sense that things ‘show up’ for you as related to these interests: as to-be-eaten, to-be-fled, to-be-mated-with and so on. Ultimately, what is good-for an animal is living her life, maintaining and reproducing herself, and so accessing the things that she needs to do this well: nutrition, safety, habitat and, for those who reproduce sexually, one or more mates.

Developing her earlier work on value, Korsgaard denies that there could be such a thing as objective goodness, where that refers to what is valuable independent of any perspective. Value is not a thing, or a property of things, that we could discover in the world. However, intersubjective value provides an alternative, and superior, way of understanding what it could mean to call something absolutely good: some things can be regarded as good from each perspective, and these things are intersubjectively good.

Thus the claim that we are, in some absolute sense, more important than the other animals would have to mean that we are more important from all points of view, including theirs. But, if this claim makes sense at all, it seems obviously false. From the point of view of the other animals, what is good is what conduces to their living the lives for which they are fit. And for most animals, human activity figures negatively in this project, if it figures at all. Even with respect to those to whom we are important – domesticated dogs, say – it is not clear what it would mean to say that we are more important to them than they are to themselves, or that our lives could matter more to them than their own lives do.

We might try the idea that we matter more than the other animals because our lives are, or can be, better than theirs. But Korsgaard argues that, like claims of absolute goodness, we can only understand such comparative claims about quality of life perspectivally. Of course a life of purely animal successes and pleasures would not be as good for us as one that contains more distinctively human achievements and flourishing. But it is meaningless to suggest that the latter life would be better for a pig or rabbit or sparrow than the best life available to their kind. Such creatures cannot enjoy that sort of life while remaining the creatures they are. There is no creature who can experience both flourishing qua human and flourishing qua sparrow, and so there is no point of view from which these two lives can be meaningfully compared. Such comparisons thus cannot rescue the claim that human beings are more important than other animals from the threat of nonsense.

It may seem to follow that we can never have reason to prioritize human lives over those of the other animals. Korsgaard evinces some sympathy with this radical conclusion, and returns to related issues in section III. But she also has two resources to resist it. First, though not absolutely more important than the other animals, we are generally more important to one another. This can ground special reasons to look out for other human beings, analogous to the reasons that a person has to care specially for her own children. Second, she holds that our lives may matter more to us than, for example, a rabbit’s life matters to it, and this could provide a reason to prefer human to other animal lives if circumstances force us to choose. But she cautions that death can also be less bad for us than it is for the other animals: a human being can regard some things as worth dying for, and our ability to conceive of ourselves as part of the ongoing project of humanity makes it the case that death is not the end for us in the same way that it is for the other animals. So there are certain sorts of cross-species value comparison that Korsgaard countenances. It is worth contemplating why she views importance-to one kind of creature as commensurate with importance-to another kind, while denying meaningful comparisons of the simpler normative notions of quality of life.

In section II, Korsgaard turns to Kantian arguments about our moral relationships to the other animals. Kant famously holds that, though we have obligations with respect to them, obligations to treat them in various ways, we do not have obligations to them. We cannot have such obligations because they are not rational creatures, and so not the sort of being to whom anything could be owed.

Korsgaard responds by distinguishing two senses in which a duty could be owed to a creature, and correlatively two senses in which we can recognize or treat another as an end in himself. First, a being may have standing to make claims and so act as co-legislator of the moral law. Second, a being may be entitled to protection by that moral law. Non-human animals are not ends in themselves in the first sense. On Korsgaard’s Kantian constructivist account, an action is permissible if, and because, it could be willed – and in this sense legislated – by all rational creatures. Animals cannot so much as consider whether their actions, or those of others, can be so willed. They are, in the sense important to Kant, both non-rational and amoral and this is why Kant says that no duties could be owed to them.

But laws can grant rights even to those who do not or cannot participate in making them. Just as one can deny that children have legislative authority, yet hold that just laws must take their interests into account, so it may be that the moral law must take the interests of all the animals into account. Then when rational creatures legislate the moral law we must regard what is good for the other animals as mattering, just as what is good for us matters. In this distinct sense we could owe duties to the other animals. Our actions could wrong them just as violating child labour laws wrongs the exploited child, not only those by whose authority the laws were put in place.

This clears conceptual space for the possibility of duties to non-human animals. To show that we do have such obligations, we need an argument that we have to will principles that protect them, or that principles that fail to do so cannot be willed as moral laws. That, in turn, requires an account of what we can will universally, one that can define permissible actions, and so cannot depend on prior notions of permissibility.

Korsgaard begins consideration of the prospects for such an account with her influential practical contradiction interpretation of Kant’s Universal Law formulation of the categorical imperative. On this view, you can will a principle as a universal law if and only if, supposing everyone acted on it, each could succeed in securing the end that it specifies. Many cases of deception, coercion and violations of norms governing contingent social practices generate practical contradictions. But this approach struggles to rule out ‘natural wrongs’, the impermissible use of brute force and violence. Using force to kill a person is almost always wrong, but it would accomplish the aim of getting him dead even if everyone who wants to kill uses force to do so. The laws of physics will work no matter how many people take advantage of them for their own ends. This weakness makes the Universal Law Formula ill-suited for thinking about duties to animals, since almost all of the wrongs that we do them are of this natural kind.

Korsgaard thus turns to Kant’s second formulation, which enjoins us to treat humanity as an end. The emphasis on humanity makes this statement of the principle prima facie unpromising as well. But Korsgaard argues that, rightly understood, Kant’s strategy for establishing the authority of the Formula of Humanity brings the other animals under its scope. On her reconstruction, the argument purports to show that we must regard it as absolutely good that any creature who has a good gets what is good-for her.

The argument takes the form of a regress on rational conditions: when we act, we treat what is good for us as if it were good absolutely. We take our end to give us reasons to act, and others reasons not to interfere and in some cases to help. Treating the end this way cannot be justified by appeal to its objective value, because nothing has value like that. Rather, just as to be permissible is to be properly willed, to be valuable is to be properly valued.

Ordinarily, you treat your ends as valuable because you care about them. This is reasonable if, but only if, that something matters to you is a reason that it should matter to anyone. And that, in turn, is true just in case you matter. So in valuing anything, we value ourselves: if anything is valuable, then we are valuable. It follows that a thing can be properly valued only if valuing it is consistent with valuing each agent, and so with the good of each. That is to say, vindicating our regard for our ends must take the form of showing that they have intersubjective value, that they can be valued from all points of view. This much is familiar from Korsgaard’s earlier work. Here she adds that human beings are not the only beings who have a point of view, and so a good. So if we treat what is good-for us as presumptively absolutely good, we must treat what is good-for another animal in the same way.

This reworking of the argument for the Formula of Humanity to include non-human animals is the most crucial part of Korsgaard’s argument, and so also raises the most questions. One constructivist approach takes the aptness of a principle to be willed as a law to render acting on that principle permissible. The Formula of Universal Law promises to furnish the account of what can be willed universally that this view needs. But, with most contemporary Kantians, Korsgaard here denies that a procedure of reasoning defined by the Universal Law Formula could alone yield all of the moral conclusions we need. In moving to the Formula of Humanity she attempts to get substantive moral conclusions from the form of moral reasoning in a different way, the substance of value from the form of valuing. But this requires an account of what can be valued intersubjectively that depends on no prior claims about value, yet yields a sufficient range of plausible conclusions about what is valuable. But if a formal standard of universal willing cannot get us to the right moral answers, why think that a formal standard of valuing from each point of view can do better?

In fact, Korsgaard’s own striking conclusion is that, given the arrangements of nature, it is not really possible to compose what is good for each creature into a single intersubjective good that we can pursue together. To take the simplest case, there is nothing that is good-for both the predator and the prey. Embrace of this conclusion provides a kind of response to the worries above, affirming the threatened indeterminacy about value rather than showing how it can be avoided. But it also raises new questions. Most pressingly, if there is no way to realize the good of all, how are we to understand the direction of the moral law?

Korsgaard’s tragic teleological view leads her to a tragic deontology that does not definitively settle this question, and culminates with rejection of the Kantian doctrine that ought implies can. We ought to value all creatures who have a good, seeking to make the world good for all of them. But since their goods are not composable, nothing would really count as achieving this morally required end, so we cannot do as we ought. This argument is a significant departure from certain Kantian sensibilities. It is also – as Korsgaard notes – reminiscent of Kant’s own argument for moral faith in God, though lacking his optimistic conclusion that we can rationally hope that a moral orderer ensures the possibility of the good outcome that we must seek.

Utilitarians attempt to solve the problem by substituting aggregation of value for intersubjective composition, allowing tradeoffs between predatory pleasures and the pain of the prey. They hold that it is better that the prey should suffer if this yields greater pleasures for the predator, or better that predators should starve if the calculation goes the other way. But Korsgaard’s rejection of comparative claims about the good, untethered from any particular point of view, rules out this resolution. Driven in part by familiar metaphysical worries, her resistance to aggregation also expresses an attractive normative ideal: everyone counts, and no one’s point of view can be accounted for just by taking it up into an aggregate of value. Korsgaard thus reaffirms a familiar Kantian conviction about the separateness of persons, now extended to a claim about the independent value of any creature with its own centre of consciousness.

The third and final section of the book casts some light on how far Korsgaard will press these anti-aggregative conclusions. Here she engages two radical positions about human interaction with the other animals: first, the claim that we should massively intervene in nature to eliminate predation thereby reducing suffering; second, the idea that we should minimize our interference with the other animals, eliminating domestic animal farming, animal experimentation and all or most pet-keeping, and reserving large tracts of the earth in which animals can pursue their good undisturbed by human activity. Korsgaard presents these conclusions, each requiring drastic but opposed reorientations of human ways of life, as a Kantian antinomy, a disturbance in our thought that she attributes to the opposition between what morality demands and what nature allows described above.

Korsgaard takes the arguments for both positions seriously, though in the end favours something closer to non-interference. She argues that, while it is true that eliminating predation would reduce future suffering, it is not clear to whom we could owe a duty to do this, or whom we could thereby benefit. The undertaking would require profoundly changing the nature of all of the animals, and this would amount to replacing them with successor species rather than improving their lives. She agrees that if we were to undertake such massive intervention, then it would be incumbent on us to make things as good as we can for the animals that we create. And she acknowledges that current human interference with the other animals puts us in the position of having, and systematically violating, this obligation to some extant animals, for instance many species bred for domestic farming. Nevertheless, it is not clear that we must undertake the even more extensive interventions envisioned.

Moreover, arguments for the second view suggest that we may not do so. Since animals cannot consent to interactions with us, it may be incumbent on us to minimize these interactions. Korsgaard follows this line of argument all the way to the thought that, given the threat that humans pose to animal habitat and the liveability of the planet, we might have an obligation to stop reproducing and allow human beings to go extinct. She withholds outright endorsement of this duty, conceding that we have an interest in the continuance of humanity, and a presumptive right to pursue what is good for us. But she warns that we can forfeit this right, and will do so if we continue to flout our obligations to our fellow creatures. She does not say what would constitute such forfeit, but suggests that we are treading dangerously close. Accepting the independent moral standing of the other animals makes it impossible to altogether deny the power of this line of thought. But it seems to me that we can take some small comfort in the hope that the argument supports, at most, a duty to contract the human population significantly, not a duty to drive ourselves to extinction.

Fellow Creatures is a model of excellence in moral philosophy that will repay careful study for years to come. It significantly advances every aspect of existing discussions about relationships between human beings and the other animals, while at the same time contributing to overlapping issues in value theory and moral psychology. It offers both intricate argumentation and a sweeping moral vision, at once tragic and summoning readers to embrace demanding moral ideals.Footnote ¹