Early Modern Perspectives on the Moral Status of Nonhuman Animals: Descartes, Kant, and Bentham
The trajectory of our anthropocentric thinking on the moral status of nonhuman animals has its roots in classical antiquity and has been guided along by the relatively unchallenged assumption that cognitive inferiority is a relevant measure of moral inferiority. The ancient Stoics and Epicureans, for example, were notoriously dismissive of the commonalities between human and animal nature, and their doctrines are equally emphatic on drawing the moral dividing line at the distinctiveness of human reason. The Stoic and Epicurean doctrines differ in principle on what they define as the source of justice, but the implications for animals are essentially the same: nonrational beings possess merely instrumental value for the sake of human ends and are categorically excluded from the sphere of moral consideration. Although we modern types have occasion to distance ourselves from the “unenlightened” views of remote thinkers, our current attitudes toward animals have been shaped by an unfortunate history of anthropocentric thinking of which we are scarcely aware.
In this connection, forming a clear conception of the overall spirit of early modern perspectives on animals is aided by considering them against the essential background of their philosophical antecedents. The focus of the present chapter is to demonstrate that early modern thinkers argue against animals on grounds that suggest a basic commitment to the criteria originally set down by the Stoic and Epicurean orthodoxies. What should hopefully become apparent in the pages to follow, then, is the ease with which even the greatest of minds succumb to the prejudices of a prevailing ideology.
One reason to deny that we have moral obligations to animals is to maintain that animals are not conscious and therefore have no well-being or interests to take into account. One such denial was developed by René Descartes, whose strict dualism and mechanistic view of nature led him to conclude that because animals lack language, they must be biological machines—devoid of any mental awareness whatsoever. In my discussion of Descartes, I draw attention to two important points. First, despite recent attempts to exonerate Descartes from the charge of holding such an implausible view, I will show that his estimation of animals as insensate automata is made clear and unequivocal by his writings. Second, I challenge a certain conventional wisdom surrounding Descartes, which holds that his principal move against animals is based on his conviction that animals are incapable of feeling pain. Descartes did not begin by looking for reasons to deny animal consciousness and pain; rather, he was driven to this conclusion by his reflections on certain philosophical problems that arose between his mechanistic science and Christian convictions. Descartes bases his commitment to the moral inferiority of animals most decisively on the application of his dualist ontology to the Stoic principle of oikeiosis, according to which nature exists for the sake of its rational components—the gods and human beings. Descartes' conception of animals as pure mechanism, coupled with his fundamental conviction that human beings, as rational souls, have a moral imperative to render themselves the “lords and possessors of nature,” is entirely in keeping with the anthropocentric spirit of Stoic cosmology.
Another reason to deny that we have moral obligations to animals is to maintain that animals warrant our moral concern only insofar as their welfare is indirectly related to the interests of human beings. In other words, we may have duties regarding animals, owing to some human interest involved, but because animals lack the relevant property that would render their interests morally significant, such duties are never discharged out of a direct concern for the animals themselves. The moral system developed by Immanuel Kant, according to which rational autonomous agents are the only kinds of beings to whom we owe direct moral obligations, holds that animals, as things, have only relative value and exist merely as means to human ends. In addition to critiquing Kant's account of indirect duties, I draw attention to those elements of his moral system that reflect an implicit commitment to the core assumptions of Epicurean contractualism. I conclude with the suggestion that, despite these unfortunate elements, the second formulation of Kant's categorical imperative can be revised to render his system amenable to the inherent value and moral personhood of nonhuman animals.
One thinker for whom the Stoic and Epicurean doctrines had little implication for the moral status of animals was Jeremy Bentham, the chief architect of the Humane Treatment Principle, which states that we have moral obligations we owe directly to animals not to cause them unnecessary suffering. Bentham holds that sentience, rather than the capacity for abstract reasoning or language, is a sufficient condition for having one's interests taken into account in the moral assessment of the consequences of our actions. The failure of previous thinkers to figure animal interests into the utilitarian calculus, according to Bentham, “degrades animals into the class of things.” The major shortcoming of Bentham's position, however, stems from his belief that it is not whether we use animals, but how we treat them in the course of that use that should command our ethical curiosity. In my discussion of Bentham, I argue that the aforementioned classification of animals that his theory purports to reject is nonetheless retained by his uncritical acceptance of the property status of animals. I also argue that Bentham is mistaken is his assertion that because animals lack an autobiographical sense of self-consciousness and are therefore subject to a lesser range of psychological afflictions, they cannot have an interest in their continued existence. In this connection, I draw attention to the insights of Plutarch, who, as an outspoken critic of the Stoics, defended the idea that sentience—properly understood as a means to an end—necessarily implies that animals have a basic interest in both the quality and duration of their lives.
Mechanistic Science and Cartesian Substance Dualism
Descartes' beliefs concerning the mental life and moral status of nonhuman animals arose, in part, from a combination of his mechanistic science, his Christian convictions, and his strict dualism. Often regarded as the father of modern philosophy and chief architect of the scientific revolution, Descartes wrote during a time when the mechanistic view of the natural world was beginning to overturn the unquestioned authority of Aristotelian scholasticism. According to mechanistic science, the workings of the physical universe are governed by the same mechanical principles that govern a clock. If you want to understand an object and explain how it works, you simply break it down into its constituent parts, analyze its properties, and conduct a series of experiments. One problem faced by this view is that consciousness, by its very nature, does not seem to fit very comfortably into a purely mechanical world. Added to this difficulty is the influence of Christian doctrine, which holds that human beings are not merely physical but are invested by God with immaterial, immortal souls. If the implication is that human beings are mere machines, then mechanistic science is faced with the problem of circumventing the heretical view that human and animal nature are of the same ontological kind, and that the human mind or soul (Descartes uses these terms interchangeably) has its genesis in the potentiality of inert matter.
The dualist view of nature that Descartes develops seeks a solution to the problem of locating human consciousness in a wholly materialistic universe. According to this view, there are two ontologically distinct and irreducible kinds of substances in the world, namely, physical bodies and immaterial minds, and that human beings are composite entities consisting of a mind and a body. Human beings may have a close association with their corporeal bodies, but they are not identical to their bodies; rather, as embodied entities created in God's image, humans are identifiable with the immaterial souls that constitute their consciousness, thought, and rational nature. By identifying the soul with consciousness, Descartes avoids the reduction of human existence to pure mechanism and provides for the coherence of the soul after bodily death. The human body and the material world it occupies is only a transitory stage in the immortal soul's journey to eternal bliss in the afterlife. In keeping with the terms of Christian doctrine, Descartes declares in a letter addressed to Plempius that his theory not only distinguishes human from animal nature but “provides a better argument against the atheists and establishes that human minds cannot be drawn out of the potentiality of matter.” Descartes' strict dualism creates a sharp and unbridgeable gap between the human soul and natural world, thereby ensuring humanity's privileged position over the rest of brute creation.
If consciousness is strictly identifiable with the human soul, what are the implications for animal nature? In a letter addressed to the Marques of Newcastle, Descartes explicitly rejects the notion that animals possess souls: “it is more probable that worms, flies, caterpillars and other animals move like machines than they all have immortal souls.” To even talk about animals as besouled beings is a serious misnomer, since “their souls are nothing but their blood.” Descartes' assertion that animals lack consciousness because they lack immaterial souls does not provide an adequate reason in support of his position, however, since it merely appeals to his religious convictions.
Descartes' most explicit and systematic denial of animal consciousness relies on the application of the principle of parsimony, commonly referred to as Occam's razor, which states that the most reasonable and preferred explanation is the one that provides the simplest account of observable phenomena under the fewest possible assumptions. An adequate scientific theory of animal nature, then, will not deny any facts regarding animal behavior, but will successfully predict and intelligibly explain those facts under the fewest assumptions possible. If we have two competing theories that explain an equal range of facts, but which differ according to the number of assumptions they make, parsimony demands that we accept the simpler of the two.
Since it is possible, in Descartes' estimation, to explain animal behavior without positing any mental awareness, such an explanation provides us with the preferred account of animal nature. The fact that animal behavior can be explained adequately in terms of mechanical processes and without reference to internal episodes such as consciousness or thought makes it unnecessary to attribute any mental awareness to animals whatsoever. The commonsensical belief that animals are conscious beings is a prejudice “to which we are all accustomed from our earliest years.” In a letter addressed to Reneri, Descartes expresses great confidence in his denial of animal consciousness, hypothesizing that if a human being raised in isolation from animals (and stripped of any anthropomorphic prejudices concerning their behavior) was suddenly confronted by one, he would no doubt conclude that animals were “automatons made by God or nature.” Despite appearances, then, animals lack any sort of conscious awareness. Animal nature is governed only by mechanical principles, since “it is nature which acts in them according to the disposition of their organs, in the same way that a clock, consisting only of wheels and springs, can count the hours and measure time more accurately than we can with all our wisdom.” Indeed, animals are organic clocks, complex clocks—clocks created by God—but clocks all the same.
Descartes' reduction of animal nature to pure mechanism is best understood in terms of the stimulus-response explanatory model that we normally apply to inanimate objects. Suppose I were to provide a stimulus by running an electrical current through a wire that is attached to a bell. The bell rings. Did the bell-wire apparatus have a subjective experience? Doubtful. We can adequately explain the causal chain that led to the ringing of the bell without attributing a mental life to the apparatus. Similarly, the stimulation of the various humors and spirits coursing through an animal's bloodstream can cause mechanically induced behavioral responses that we normally associate with pain, fear, hunger or excitement; however, absent further evidence, we have no grounds for making the inference that animals consciously experience these states.
If animals lack consciousness, can they still have sensations? Can they still “feel” their pain, hunger, excitement, and so forth? According to the terms of Descartes' strict dualism, the mind, as an immaterial substance, is a “thing which thinks,” and a thing which thinks “understands, affirms, denies, imagines and has sensory perceptions.” These conscious intentional states are different “ways of thinking,” and they all have their source in the rational human soul. Human thought is governed by “the operations of the soul, so that not only meditations and acts of will, but the activities of seeing and hearing and deciding on one movement…also depend on the soul.” In a letter addressed to Henry More, Descartes acknowledges that animals are certainly “alive” and have “sensations,” provided that the former is regarded “as consisting simply in the heat of the heart,” and the latter “insofar as it depends on a bodily organ.” These passages should dispel any lingering doubts concerning Descartes' unequivocal denial of animal sentience. Animals are purely mechanical and corporeal, completely lacking in thought; they have no experiential or perceptual capacities whatsoever.
Although human and animal bodies are essentially the same, the reason why human beings feel pain and animals feel none is that human reactions to sensations are associated with the immaterial mind and are therefore accompanied by inner conscious experiences, whereas animal bodies under similar circumstances experience nothing but the mechanistic motion of the various humors and spirits that stimulate the “corporeal organs effected.” This is the case because animals, being no different from clocks or bell-wire apparatuses, are wholly incapable of thought. On this assumption, then, human sensation exists solely in the thinking mind and is different in kind from animal sensation. We have been misled by our anthropomorphic prejudices to draw analogies between human and animal nature and to make the erroneous inference that animal automata are sentient beings with subjective lives. The textual support for Descartes' unequivocal denial of both animal consciousness and pain is abundant and unmistakable.
Descartes' underlying assumption that the faculties of abstract reasoning and language constitute the outward marks of the mental and therefore provide the essential distinction between human and animal nature is made apparent in an exchange with two of his critics, Pierre Gassendi and Julien Offay de La Mettrie, both of whom challenge the explanatory power of the mechanistic view when applied to animal nature.
Gassendi raises the objection that animals not only experience some awareness but exhibit a kind of reasoning that is peculiar to their species. The differences between human and animal nature are primarily differences of degree, not kind. In response, Descartes mostly reiterates his conviction that none of the outward behaviors of animals lead him to posit mind or reason animals; that animals sometimes act in accordance with reason rather than through or for it is entirely consistent with his hypothesis. Reason is a “universal instrument” that enables the human agent to respond to the “contingencies of life” with complex and novel behavior; animal machines, in contrast, act not through reason but from the disposition of their organs.
La Mettrie challenges Descartes by arguing that the mechanistic view casts us into a greater skeptical bog than Descartes realizes. Since the physiological processes in virtue of which humans and animals react to various stimuli are essentially the same, parsimony demands that we explain human nature by applying the same mechanistic principles we use to explain animal behavior. Of course, the implication that human mental life consists of nothing more than the mechanical motion of animal spirits in the human nervous system is absurd. If La Mettrie is correct, the mechanistic explanation is self-defeating; it undercuts its own authority and proves itself inadequate as the most reasonable explanation of human and animal behavior.
Descartes' comments in Discourse V anticipate this objection to his reasoning. The main reason why the mechanistic explanation of behavior applies to animals but not to human beings is because humans exhibit one behavioral characteristic that is most expressive of an inner mental life: a developed and communicable language. Language is the faculty in virtue of which human beings can communicate their detailed thoughts and experiences of pain to one another, whereas “animals are incapable of arranging various words together and forming an utterance from them in order to make their thoughts understood.” Although animals may produce gestures and utterances that function to express their reactions to various stimuli, and although magpies and parrots have speech-organs that can mimic our language, declarative speech, which is unique to humans, is fundamentally different in kind. For Descartes, the absence of declarative speech in animals is explainable only in terms of the absence of animal thought.
Since the faculties of abstract reasoning and language are coextensive with the possession of the rational soul—the source of consciousness and sensation—and since animals exhibit neither faculty, they must, on Descartes' account, be mindless machines. The difference between Descartes' estimation of animal nature and those of his critics who attribute mind to animals does not arise from any disagreement regarding the observable facts of animal behavior; rather, Descartes' commitment to mechanistic science and his strict dualism return us to the principle of parsimony and his hypothesis that animal nature, understood as pure mechanism, provides the most sensible and impartial explanation of the facts.
If Descartes is correct that animals are no different from inanimate objects, then inquiring into their moral status would be pointless; therefore, we should briefly consider whether his view of animal nature is the least bit plausible by contemporary standards. First, we have no reasonable grounds for assuming that the capacity for declarative speech is a necessary condition for consciousness; to argue otherwise, in light of what we now know, simply begs the question. Second, the implication that human infants lack minds prior to acquiring a language borders on the perverse. Indeed, any argument that proposes otherwise must intelligibly explain how infants come to learn a language. Third, we have good reasons to believe that animal consciousness obtains independently of the ability to use language. The obvious structural similarities between humans and animals, coupled with evolutionary theory and a wealth of ethological evidence, demonstrates that we have no reason to lack confidence in our inference that animals are sentient beings.
Reason over Passions and Lordship over Nature
The standard interpretation of Descartes' principal move against the moral status of animals can now be summarized as follows: since animals lack language, they cannot be conscious; since they lack consciousness, they cannot feel; and since they cannot feel, they cannot have sensations, including pain; animals are mindless machines, and their cries are nothing more than mechanically induced responses to aversive stimuli. In a letter addressed to Henry More, Descartes remarks that “my opinion is not so much cruel to animals as indulgent to men…since it absolves them from the suspicion of crime when they eat or kill animals.” Accordingly, we are morally justified in using animals without any concern for the pain we might be causing them and can perform all sorts of hideous experiments on them in order to advance our scientific knowledge. Descartes' vivid descriptions of vivisection on live animals, and the enthusiastic tone with which he recounts his findings, suggest not only that he performed such experiments, but did so without any moral qualms whatsoever.
But however advantageous the reduction of animal nature to pure mechanism might have been for such purposes, the standard interpretation is wrong to imply that Descartes bases his commitment to the moral inferiority of animals most decisively on his belief that animals are incapable of feeling pain. As previously stated, Descartes was driven to this conclusion by his reflection on certain philosophical problems that arose between his mechanistic science and strict dualism, and his reduction of animal nature to pure mechanism is one attempt at a solution. Although the standard interpretation correctly traces the line of reasoning for Descartes' denial of animal pain, his emphasis on moral maturation in The Passions of the Soul, coupled with his uncritical acceptance of the Stoic criterion of reason, form the fundamental basis for his principal move against the moral status of animals.
One key passage in the Passions of the Soul reveals a glimpse of Descartes' conception of morality: “I see only one thing in us which could give us good reason for esteeming ourselves, namely, the exercise of our free will and the control we have over our volitions…it renders us in a way like God by making us masters of ourselves.” To qualify as a being of moral worth is to have the self-determination to overcome one's bodily passions, which, in turn, requires the sophisticated conceptual ability to bring one's volitions in alignment with what rational principles demand. The possession of the rational soul is what enables human beings to supplant their passions, contemplate the divine, and pursue moral truths. The ontological status of humans as embodied rational souls is directly related to their superior moral status, since their nature most resembles the perfected nature of God in whose image they were created. Irrational animals, in contrast, as pure mechanism or corporeality, are of the lowest order of being and are not worthy of moral respect. Since “every man in indeed bound to do what he can to procure the good of others,” and since one “who is of no use to anyone else is strictly worthless,” it follows that animals are categorically excluded from the moral community and may be used as mere means for human ends. This is so because all and only human beings, by virtue of their free-will, can gain complete mastery over their passions and promote the general good. By circumscribing human reason as the moral boundary against which everything else is rendered worthless, Descartes' view is entirely in keeping with those of his philosophical forebears. Human beings have the prerogative to manipulate nature and exploit animals as resources to promote the general welfare. Descartes is explicit in his conviction that it is incumbent on human beings, as moral agents, to render themselves the “lords and possessors of nature,” which is the chief good of human life.
The parallelism between Descartes' mastery of nature ideology and Stoic cosmology is considerable, indicating that his commitment to the criterion of reason as a necessary condition for moral worth is but another instance of a tradition of anthropocentric thinking that hearkens back to classical antiquity. Both Descartes and the Stoics subscribe to a kind of perfectionism according to which the purpose of the moral life is to perfect one's soul and exercise one's reason to the fullest extent possible. The Stoics developed their doctrine of the logos, whereby nature advances in hierarchical degrees toward human rationality and its contemplation of the divine, and according to which animal nature, situated far below this pinnacle, occupies a fundamentally inferior place in the cosmic scheme. The logos is a rational cosmic principle that only beings capable of reasoning have the ability to contemplate. Irrational animals, in contrast, whose lives are oriented exclusively on self-preservation and whose natures are ruled by the “passions,” take no part in the logos. This fundamental asymmetry between human and animal nature entitles human beings to use animals to satisfy their material needs.
Both Descartes and the Stoics appeal to a conception of divine providence, according to which God, or the gods, created the world for the sake of human beings. Irrational animals, like any other resource, have merely instrumental value for the satisfaction of human ends. Just as the Stoics declare that our mastery over nature furthers its teleological design, so Descartes declares that rendering ourselves the lords and possessors of nature fulfills our God-ordained prerogative to advance the sciences, especially medicine, for the sake of the general good. The Cartesian conception of the cosmos and our place in it, like the Stoic conception, views humanity as fundamentally discontinuous with the natural order—as quasi-divine agents thrust into an alien medium.
Descartes' remark in The Passions of the Soul that all and only rational beings are worthy of esteem reflects the Stoic principle of oikeiosis, a process whereby human beings come to regard one another as kin and equal recipients of justice in virtue of their shared rational nature. We can extend justice only to those beings with whom we share kinship relations, and since no beings apart from humans possess reason, it follows that we have no moral duties to animals whatsoever.
The main project of Kant's Grounding for the Metaphysics of Morals is to develop a clear understanding of our ethical duties by establishing a “supreme moral principle” as the basis for morality. Principles based on empirical considerations, such as self-interest or the best aggregate consequences, cannot provide a secure foundation for morality, since they are dependent on particular situations and have only limited applicability. The supreme principle must be “a priori” in the sense that it must obtain independently of experience, be based solely on the concepts of reason, and command obedience from rational agents at all times in all places. Moral principles are universally valid only if they are based on the intrinsic authority of a priori concepts that all and only rational beings can ascertain. With these stipulations in mind, Kant's criteria for moral duties can be summarized as follows: the moral quality of an action is judged not according to the action's consequences, but according to the motives that caused the action; therefore, an action is moral if and only if it is undertaken with pure motives in mind; that is, from a sense of duty and respect for the moral law alone.
The general formula that best meets these criteria is the categorical imperative, which states that we should: “act in such a way that we could will that the maxim of our action become a universal law.” The second formulation of the categorical imperative states that one should “act in such a way that he treat humanity, whether in his own person or in the person of another, always at the same time as an end and never simply as a means.” Rational agents violate the categorical imperative when they apply a standard to their own actions that they would not endorse as a universal law for the actions of everyone else. They must not treat other rational agents as mere means to their own purposes, but acknowledge their independent value as “ends-in-themselves.”
Willing, Autonomy, and Inherent Value
Kant's perspective on the moral status of animals is based most decisively on his conception of the faculty of willing: “a rational being has the power to act according to his conception of laws; i.e., according to principles, and thereby has he a will…the derivation of actions from laws requires reason.” Having a will is what enables rational agents to choose courses of action in pursuit of those predetermined goals that render them citizens in “the kingdom of ends.” Both humans and animals have desires that compel them to action, but only rational agents, by means of the freedom of their will, can withhold their desires and bring general principles to bear in considering their maxims. The ability of rational agents to stand back at a reflective distance from their situations and universalize the maxims of their actions in accordance with the categorical imperative forms the basis of their autonomy and inherent dignity:
“Every rational being exists as an end in himself, not merely as a means to be arbitrarily used by this or that will..beings whose existence depends not on our will but on nature have, nevertheless, if they are not rational beings, only a relative value as means and are therefore called things..rational beings are called persons inasmuch as their nature already marks them out as ends in themselves.”
Kant's conception of personhood identifies a category of morally considerable beings who have inherent value as ends-in-themselves. Since all and only human beings have an autonomous will, it follows that all and only human beings are persons. By drawing the moral dividing line at the faculty of reason, Kant follows in the tradition of reducing animals to the status of things—as mere means to the satisfaction of human ends.
Indirect Duties to Animals
In the Lectures on Ethics, Kant explicitly rejects the notion that animals warrant our moral concern in any straightforward sense; rather, animals are morally considerable only insofar as their welfare is indirectly related to the interests of human beings. Kant is not implying that we should never figure animals into the moral assessments of our actions, but he does make it clear that our duties regarding animals are never discharged out of a direct concern for their interests:
“If a man has his dog shot, because it can no longer earn a living for him, he is by no means in breach of any duty to the dog, since the latter is incapable of judgment, but he thereby damages the kindly and humane qualities in himself, which he ought to exercise in virtue of his duties to mankind. ..when anatomists take living animals to experiment on, that is certainly cruelty, though there it is employed for a good purpose, because animals are regarded as man's instruments…our duties toward animals, then, are indirect duties toward humanity.”
Kant acknowledges that animals are sentient beings with interests of their own, but because they lack self-consciousness and are incapable of making moral judgments, they exist “merely as a means to an end. That end is man.” Any restrictions regarding our proper use and treatment of animals come into existence only when our actions carry adverse effects for other rational agents.
To better understand Kant's account of indirect duties and its implications for the moral status of animals, consider some examples of our duties regarding public and private property. I have a moral obligation not to deface the memorial statue in your town square, since doing so might upset you and offend public sentiments. I also have a moral obligation not to destroy your car, since doing so would violate your property rights and thereby do you harm. According to Kant, our indirect duties regarding animals come into existence for precisely the same reasons. I have a moral obligation to refrain from harming your pet, since doing so would damage your animal property and exhibit those traits of character that society does not wish to promote. I cannot directly “wrong” your pet, however, anymore than I can directly “wrong” your car. Both are merely things, according to Kant, so I have not failed in my duties toward either; rather, I have harmed you, or harmed society, or degraded my own moral character. By mistreating animals for fun, I incline myself toward violence in my dealings with others humans. Although there can be little doubt that fostering kindness toward animals cultivates moral character, Kant's indirect duty theory ultimately denies any meaningful moral status to animals.
Incoherence and Marginal Cases
There is an uneasy tension between Kant's explicit denial of our direct duties toward animals and his circuitous attempt to grant them something like a moral standing. This tension indicates that he finds something deeply wrong with the notion that we can treat sentient beings like inanimate objects, but he is committed to the idea that only rational agents warrant our direct moral concern. Indeed, the moral distinction he draws between what is “inherently wrong” and what is “cruel” seems arbitrary rather than rationally grounded. If animals, as things, are not the objects of our moral concern, then how is our mistreatment of them any more “cruel” than kicking inanimate objects? Kant claims that such behavior is cruel because it displays those traits of character that society disvalues and discourages. This is incoherent. We cannot simultaneously hold in any meaningful way that animals are our resources and that our mistreatment of them has moral consequences for human beings. Furthermore, a convincing argument could be made that the enjoyment we derive from eating animals is as cruel as the enjoyment we derive from forcing them to fight one another. On the assumption that there is no morally relevant distinction between the two, Kant's indirect duty theory turns out to be nothing more than an endorsement of the status quo. The restrictions we impose on the proper use and treatment of animals are generated by whatever society happens to regard as an unacceptable form of animal exploitation. Kant's theory cannot have it both ways: either the mistreatment of animals is immoral because it wrongs animals directly, or such mistreatment raises no ethical concerns whatsoever. The fact that Kant even addresses the problem of animals suggests that he sees something deeply disturbing in the notion that we can completely disregard their interests, but because his moral theory presupposes that animals are things, he is unwilling to concede that we can wrong them in any straightforward sense.
Another difficulty faced by Kant's theory concerns the question of how moral standing is to be extended on an equal basis to “marginal cases,” such as human infants and the mentally impaired, who lack rationality and are incapable of moral choice.
The “Argument from Marginal Cases” can be schematized as follows:
1. If we have no direct moral obligations to animals, then we have no direct moral obligations to marginal cases.
2. We do have direct moral obligations to marginal cases.
3. Therefore, we do have direct moral obligations to animals.
Opponents to the argument from marginal cases can attempt to refute it in two ways. First, they can deny premise (1) by arguing that all and only human beings possess some property (reason, self-consciousness, language, etc.) that renders their interests directly morally considerable; however, it is not the case that all and only human beings possess these properties, nor is it clear why these properties should be considered morally relevant. Second, opponents can deny premise (2) by maintaining that marginal cases are not directly morally considerable and may be treated as we currently treat nonhuman animals. Virtually no one accepts this conclusion, and for those few who do, I doubt there is much I could offer them by way of persuasion. When we harm an infant or mentally impaired human, we have failed in our moral duties, not because we have frustrated the interests of their caretakers, but because we have wronged them directly by degrading them to the status of things. Some opponents claim that when the actual number of marginal cases is realized, it is not so counterintuitive to conclude that the remaining individuals have no moral status. I reject this view. The number of marginal cases has no direct bearing on the moral matter. The claim that harming marginal cases is of vanishing moral significance because they are few in number is both unconvincing and unpleasant. It is a refusal to acknowledge the problem. Once the argument from marginal cases is appreciated, Kant's account of our indirect duties to animals turns out to be a serious flaw in his theory.
In her book The Three Frontiers of Justice, Martha Nussbaum states that the social contract tradition “conflates two questions that are in principle distinct: by whom, and for whom, are society's basic principles of justice designed?” Having dispensed with any concept of pre-political rights, the tradition has created “a general image of society as a contract for mutual advantage” and personal gain.
I will now attempt to demonstrate the following two points: although Kant rejects the contractualist conception of morality, his theory reflects an implicit commitment to its core assumptions in connection with the moral status of animals; second, I will diagnose the categorical imperative as suffering from the same conflation quoted above and venture to provide a viable alternative.
The contractualist conception of morality as wholly conventional and grounded in calculating self-interest is one that Kant's theory categorically rejects. Fundamental for Kant is the conviction that our duties be discharged without any considerations of mutual advantage or personal gain. Contractualists do not undertake their actions from a sense of duty and respect for the moral law alone; rather, the only significance contractualists attach to mutual agreements, and to social justice generally, is how effectively they advance their interests. Indeed, if the situation between two parties is so asymmetrical as to disallow mutually advantageous cooperation, contractualism places no constraints on the stronger party from dominating the weaker.
Kantian agents elevate themselves above the state of nature when they embrace the demands of morality unconditionally and discharge their duties without consideration for what they stand to gain from the outcome. When Kant considers the place of animals in his theory, however, the conclusion he reaches returns us to the state of nature that the kingdom of ends seeks to overcome. By applying a different standard to ourselves when the objects to which our actions are directed are beings with whom we cannot procure some mutual advantage, we violate the categorical imperative by accepting the self-serving terms of Epicurean contractualism.
Rethinking the Categorical Imperative
Epicurean contractualism and its philosophical successors assume that the subjects for whom the basic principles of justice are designed are strictly identifiable with the contracting parties who design the principles. The principles of justice are designed to secure the interests of those subjects whose capacities lie within normal range with those of the contracting parties (rational beings). Contractualism thereby conflates the devisers of the principles with the objects to which the principles ought to apply.
The categorical imperative suffers from a similar conflation. Kant confuses the subjects of the categorical imperative with the objects to which the categorical imperative ought to apply. Despite this considerable flaw, Kant's moral theory still provides the firmest foundation for the basic right of all sentient beings not be treated exclusively as means to an end. In particular, I suggest the following revision for the second formulation of the categorical imperative: always act in such a way that you treat sentience, whether in your own person or in the person of another, always at the same time as an end and never simply as a means. Personhood therefore identifies a category of morally considerable sentient beings who possess value in their own right.
In An Introduction the Principles of Morals and Legislation, Bentham presents his “greatest happiness principle” as the correct standard for determining the moral quality of our actions in every situation. The happiness principle holds that our moral choices are right or wrong according to the consequences of our actions alone, and that we should choose that action which results in the greatest happiness for all those individuals whose interests are affected by the outcome. Since pleasure is inherently good, and since pain is inherently bad, whatever motives we may have for our actions are judged only according to the consequences they produce. The moral quality of an action, therefore, is determined by its utility alone.
In a pivotal passage confined to a footnote, Bentham outlines the basis for the Humane Treatment Principle, which establishes that we have moral obligations we owe directly to animals not to cause them unnecessary suffering:
“What else is it that should trace the insuperable line? Is it the faculty of reason, or, perhaps, the faculty of discourse? But a full-grown horse or dog is beyond comparison a more rational, as well as more conversable animal, than an infant of a day, a week, or even a month old. But suppose the case were otherwise, what would it avail? The question is not, Can they reason? nor, Can they talk? but, Can they suffer?”
In contrast to previous thinkers, Bentham holds that sentience (the capacity to experience pain and pleasure) is the only characteristic that is necessary for having one's interests taken into account in our moral reflections. He rejects the view that language and abstract reasoning are morally relevant, since neither faculty is linked to suffering. The notion that animals should be excluded from the moral community simply because they are not rational is arbitrary and degrades animals “into the class of things.” In recognizing the odious link between human slavery and our mistreatment of animals, Bentham distinctly has in mind the principle of equal consideration, which demands that we treat like cases alike and balance their interests accordingly unless there is a morally sound reason not to do so.
Self-Consciousness and Continued Existence
Bentham's position on the moral status of animals signaled a historical turn against the traditional prejudice that only rational beings warrant our direct moral concern; however, in the same passage in which he claims that the capacity for suffering is the moral baseline for inclusion in the utilitarian calculus, Bentham draws considerable limits on the extent to which the lives of animals ultimately matter:
“If the being eaten were all, there is very good reason why we should be suffered to eat such of them as we like to eat: we are the better for it, and they are never the worse. They have none of those long-protracted anticipations of future misery which we have. The death they suffer in our hands commonly is, and always may be, a speedier, and by that means a less painful one, than that which would await them in the inevitable course of nature. If the being killed were all, there is very good reason why we should not be suffered to kill such as molest us: we should be the worse for their living, and they are never the worse for being dead. But is there any reason why we should be suffered to torment them? Not any that I can see.”
Lacking the capacity for abstract reasoning, animals have no sense of identity over time and possess a mental awareness that is confined to a continuous present. They have no recollections of their past and no aspirations for the future. In short, they cannot have an interest in their continued existence. They are wholly indifferent to the durations of their lives and care only for how well they are treated by human beings. When we kill animals for food and other uses, we do them a favor of sorts, since we provide for their needs in the short-term and spare them the harms that await them in nature (it evidently did not occur to Bentham that the domesticated animals we routinely exploit were not removed from the wild but were bred by human beings). Since animals have no interest in remaining alive, we may use them as we use any resource, provided that the suffering we impose on them is minimized. For Bentham, the moral question turns not on whether we can use animals, but on how we should treat them.
There are some serious flaws in Bentham's assumption that because animals cannot desire, anticipate, or plan for their future, they cannot have an interest in their continued existence. Although science cannot give us a definitive answer on the precise nature of animal mentation, some of the behaviors we observe in animals cannot be adequately explain without reference to something like long-term desires. However, for the moment, let us suppose that Bentham is correct; that is, let us suppose that no animals apart from human beings have the sophisticated conceptual ability to desire, anticipate, or plan for their future. The conclusion Bentham draws from this consideration is that animals cannot have an interest in their continued existence; rather, they can only have an interest in avoiding unnecessary suffering. In the discussion to follow, I give three reasons for why I believe Bentham is mistaken.
The first reason concerns the nature of what it means to have an interest. One common understanding of interests appeals to the close connection between desires and interests. In other words, if I have a desire to remain alive, then it follows that I have an interest in remaining alive. Animals, in contrast, cannot desire or anticipate the future; therefore, animals cannot have interest in remaining alive. We might call this the “desire-based theory of interests.” Fortunately, there is another common way of understanding interests, call it the “recognition-based theory of interests,” that makes no appeal to desires or aspirations.
If Jane has an interest in x, we normally acknowledge that Jane desires x; however, we do speak of some things being in Jane's best interests, whether she desires those things or not. In other words, we typically recognize that an individual's life, bodily integrity and mental well-being are in his or her best interests, even if these things are not desired by them. Similarly, our pets may not possess the sophisticated conceptual ability to desire or plan for their futures in the sense that we do, but, all other things being equal, we still typically recognize that it is in their best interest to remain alive. The recognition-based theory demonstrates that interests can obtain independently of and are not necessarily derived from desires. Having an interest in one's continued existence does not necessarily require that one have the ability to understand calendars and contemplate future events.
One immediate objection that might be raised is that the recognition-based theory of interests lands us into a slippery slope. If all it takes for something to have morally considerable interests in the sense I have articulated it is our recognition, then certainly plants have an interest in remaining alive, and even cars have an interest in remaining well-oiled. But no one would maintain that plants and cars warrant our direct moral concern; therefore, the recognition based-theory is indefensible. This objection misses one key distinction between animals, plants, and inanimate objects: animals have an experiential welfare in virtue of being sentient. To be a sentient being is to be the subject of an experiential welfare that can be enhanced or frustrated by pleasures, afflictions, and deprivations. Sentience is the minimal prerequisite for having interests at all. If a being is not sentient, then there is nothing to take into account. Plants and cars are “things.”
Keeping in mind the recognition-based theory of interests, consider the following example, which expands on the preceding point. John suffers from a condition known as “transient global amnesia.”  He has no recollection of his past and no thoughts about his future. He is mystified by his own reflection. John lives in a “continuous present.”
However peculiar John's condition might seem, virtually no one would maintain that he has no interest in remaining alive, or that it is morally acceptable to exploit him for whatever purpose we see fit. Although John's condition may justify differential treatment in some situations, we would not be justified in treating him exclusively as a means to our ends. We recognize that John has an interest in his continued existence, even though he is incapable of desiring or planning for the future.
Third, consider a line of argument advanced by Plutarch. We have good reasons to believe that sentience, by its very nature, logically implies having an interest in remaining alive, since ““nature, which they rightly say, does everything with some purpose and to some end, did not create the sentient creature merely to be sentient when something happens to it…there are in the world many things friendly to it, many also hostile.” Plutarch understands that sentience is not an end-in-itself, but is a means to the end of remaining alive. Sentience logically implies the possession of “some perception, hearing, seeing, imagination, and intelligence, which every creature receives from Nature to enable it to acquire what is proper for it and to evade what is not.” Sentient animals use their sensations to escape those situations that threaten their lives and pursue those situations that enhance their lives. What Bentham fails to acknowledge is that not all harms hurt. Death is the greatest possible harm that one can inflict on the experiential welfare of any sentient being because it forecloses all opportunities for satisfaction, and that is why sentient beings have a basic interest in both the quality and duration of their lives. Gary Francione, who also views sentience as a means to an end, advances a contemporary version of Plutarch's argument:
“Sentience is not an end-in-itself; it is a means to the end of staying alive…sentience is what has evolved in order to ensure the survival of complex organism. To deny that a being who has evolved to develop a consciousness of pain and pleasure has no interest in remaining alive is to say that conscious beings have no interest in remaining conscious.”
Regardless, common sense tells us that if an animal struggles against a threat to its life and pursues situations that enhance its life, then that animal does desire to remain alive, even if that desire cannot be expressed or thought about through human language.
The Property Status of Animals
Although Bentham changed our moral thinking about animals and urged the enactment of animal welfare laws, such as anticruelty statutes, that attempt to regulate our use and treatment of animals, the operation of those laws have failed to provide any meaningful protection for animal interests. The human treatment principle, which incorporates the principle of equal consideration, and which requires that we balance the supposed conflicts between human and animal interests to determine whether their suffering is necessary, is rendered meaningless by the fact that welfare laws presuppose the property status of animals. The balancing “choice” to be made between human and animal interests is illusory, since their fates have already been predetermined by their property status. Animals are commodities that we own in the same way that we own inanimate objects, and they have no value aside from that which their property owners choose to given them. To say that some humans regard their pets as members of their families is to say that they regard them as having a higher than market value, pure and simple. Since animals are regarded as human property, their interests may be disregarded whenever it is in the interests of the property owner to do so. To the extent that Bentham's theory asks whether the pain and suffering we impose on animals is necessary, “the inquiry is limited to whether the particular use is in compliance with the customs and practices of property owners who, we assume, will not inflict more pain and suffering on than is required for the purpose.” Our infliction of suffering on animals raises moral and legal concerns only when it does not conform to our socially accepted forms of institutionalized animal exploitation. Although Bentham's theory expresses its disapproval of the unnecessary suffering of animals, virtually none of our uses of animals, for reasons of pleasure, amusement, and so forth, can be characterized as “necessary” in any meaningful sense. The animal welfare laws that were intended to protect animal interests have managed only to facilitate our exploitation of animals in a more socially acceptable and economically efficient way. From both a logical and practical standpoint, then, Bentham is fundamentally mistaken in his conviction that the principle of equal consideration can apply to animals even if they are our property. Bentham's theory simply cannot provide meaningful protection for animal interests.
The grounds on which early modern thinkers argue against the moral status of animals represent a continuity and adherence to the traditional prejudices of the Stoic and Epicurean doctrines. Descartes inherits from his Stoic and Christian forebears the idea that the world exists for the sake of its rational components—an idea which informs the terms of his strict dualism as regards the moral status of animals. By conflating the authors of the categorical imperative with the objects to which the categorical imperative ought to apply, Kant inherits the core assumptions of the contract tradition that his theory purports to reject. Bentham comes close to meriting animals a meaningful moral status, but his criterion of self-consciousness and indifference to the property status of animals reflects his adherence to the underlying assumption that cognitive inferiority is a relevant measure of moral inferiority. Combining the utilitarian view that moral status comes from sentience with the revised version of the second formulation of the categorical imperative provides the firmest foundation for our duties of justice toward animals. Seeing this mission through will require shifting the paradigm away from treatment and toward the abolition of their property status.
Bentham, Jeremy. An Introduction to the Principles of Morals and Legislation. New York: Hafner/MacMillian, 1948.
Descartes, Rene. The Philosophical Writings of Descartes. Edited by John Cottingham et al. 3 vols. Cambridge: Cambridge University Press, 1984-1991.
Francione, Gary L. Introduction to Animal Rights: Your Child or the Dog? Philadelphia: Temple University Press, 2000.
----Animals as Persons: Essays on the Abolition of Animal Exploitation. New York: Columbia University Press, 2008.
Kant, Immanuel. Grounding for the Metaphysics of Morals. Translated by James W. Ellington. Indianapolis: Hackett, 1981.
----Lectures on Ethics. Edited by Peter Heath and J. B. Schneewind, translated by Peter Heath. Cambridge: Cambridge University Press, 1997.
Nussbaum, Martha C. Frontiers of Justice: Disability, Nationality, and Species Membership. Belknap Press: Mass, 2006.
Plutarch. Moralia Volume XII. Trans. Harold Cherniss and William C. Helmbold. Cambridge, Mass.: Harvard University Press, 1995.
Porphyry. On Abstinence from Killing Animals. Trans. Gillian Clark. New York: Cornell University Press, 2000.
Regan, Tom. The Case for Animal Rights. 2nd ed. University of California Press, 2004.
Steiner, Gary. Anthropocentrism and its Discontents: The Moral Status of Animals in the History of Western Philosophy. Pittsburgh: University of Pittsburgh Press, 2005.
 Descartes, Rene. The Philosophical Writings of Descartes. Edited by John Cottingham et al. 3 vols. Cambridge: Cambridge University Press, 1984-1991, (I: 142).
 Bentham, Jeremy. An Introduction to the Principles of Morals and Legislation. New York: Hafner/MacMillian, 1948, p. 310.
 Descartes, Rene. The Philosophical Writings of Descartes. Edited by John Cottingham et al. 3 vols. Cambridge: Cambridge University Press, 1984-1991, (I: 141).
3 Ibid, (III: 62).
 Ibid, (III: 366).
 Ibid, (III: 362).
 Ibid, (III: 365).
 Ibid, (III: 99).
 Ibid, (I: 141).
 Ibid, (II: 19).
 Ibid, (III: 56).
 Ibid, (III: 54).
 Ibid, (III: 366).
 Ibid, (II: 189).
 “Although many animals show more skill than we do in some of their actions, yet the same animals show none at all in many others; so what they do better does not prove that they have intelligence, for if it did then they would have more intelligence than any of us and would excel in anything. It proves rather that they have no intelligence.” Ibid, (I: 141).
 Ibid, (I: 140).
 Regan, Tom. The Case for Animal Rights. 2nd ed. University of California Press, 2004, p. 9.
 Descartes, Rene. The Philosophical Writings of Descartes, (I: 140).
 Ibid, (III: 366).
 Ibid, (III: 80-2).
 Ibid, (I: 384).
 Ibid, (I: 348).
 Ibid, (I: 145).
 Ibid, (I: 142-3).
 “By “morals” I understand the highest and most perfect moral system, which presupposes a complete knowledge of the other sciences and is the ultimate level of wisdom. Now just as it is not the roots or the trunk of a tree from which one gathers fruit, but only the ends of the branches, so the principal benefit of philosophy depends on those parts of it which can be learnt last of all” (I: 186). The philosophical “fruits” of the metaphorical tree are mechanics, medicine, and morals, which, for Descartes, are taken to be coextensive. Humanity's technological imperative to gain complete mastery over nature for the sake of scientific progress has an unmistakable moral dimension.
 Kant, Immanuel. Grounding for the Metaphysics of Morals. Translated by James W. Ellington. Indianapolis: Hackett, 1981, p. 36.
 Ibid, p. 36.
 Ibid, p. 29.
 Ibid, p. 35
 Lectures on Ethics. Edited by Peter Heath and J. B. Schneewind, translated by Peter Heath. Cambridge: Cambridge University Press, 1997, p. 212-13.
 Ibid, p. 212.
 Nussbaum, Martha C. Frontiers of Justice: Disability, Nationality, and Species Membership. Belknap Press: Mass, 2006, p. 16.
 Ibid, p. 14
 “Now if people had been able to make a contract with other animals, as with other human beings, not to kill and to be killed indiscriminately by us, it would have been fine to push justice to that point, because it would tend to safety. But since it was an impossibility for that are not receptive to reason and share in law, this method could not be used to secure our advantage in respect of safety from other animate creatures…that is why the only way to achieve such safety as is possible is to take license which we now have to kill them.” Porphyry. On Abstinence from Killing Animals. Trans. Gillian Clark. New York: Cornell University Press, 2000, (1.12. 6-7), p. 36.
 Bentham, Jeremy. An Introduction to the Principles of Morals and Legislation. New York: Hafner/MacMillian, 1948, p.1.
 Ibid, p. 310.
 Francione, Gary L. Introduction to Animal Rights: Your Child or the Dog? Philadelphia: Temple University Press, 2000, p. xxv.
 Ibid, p. 310.
 Animals as Persons: Essays on the Abolition of Animal Exploitation. New York: Columbia University Press, 2008, p. 144.
 Plutarch. Moralia Volume XII. Trans. Harold Cherniss and William C. Helmbold. Cambridge, Mass.: Harvard University Press, 1995, (960E), p.329.
 Ibid, (960E), p. 329.
 Francione, Gary L. Introduction to Animal Rights, p. 157.
 Ibid, p. 36.