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