Kennedy Institute of Ethics Journal 9.4 (1999) 309-324

The Failure of Theories of Personhood

Tom L. Beauchamp

Abstract:The belief persists in philosophy, religion, science, and popular culture that some special cognitive property of persons like self-consciousness confers a unique moral standing. However, no set of cognitive properties confers moral standing, and metaphysical personhood is not sufficient for either moral personhood or moral standing. Cognitive theories all fail to capture the depth of commitments embedded in using the language of "person." It is more assumed than demonstrated in these theories that nonhuman animals lack a relevant form of self-consciousness or its functional equivalent. Although nonhuman animals are not plausible candidates for moral personhood, humans too fail to qualify as moral persons if they lack one or more of the conditions of moral personhood. If moral personhood were the sole basis of moral rights, then these humans would lack rights--and precisely for the reasons that nonhuman animals would.

What it is to be a person is a principal topic of metaphysics. Ideally, a pure metaphysical theory expresses a morally detached interest in how to distinguish persons from nonpersons. However, the metaphysics of persons has often been put to work to defend a preferred moral outcome, placing metaphysics in the service of ethics. Metaphysics is invoked to inquire whether individuals have rights and whether the theory of persons can address practical problems of abortion, reproductive technology, infanticide, refusal of treatment, senile dementia, euthanasia, the definition of death, and experimentation on

In light of the different objectives of theories of persons, clarification can be introduced by a distinction between metaphysical and moral concepts of persons. 1 As I draw the distinction, metaphysical personhood is comprised entirely of a set of person-distinguishing psychological properties such as intentionality, self-consciousness, free will, language acquisition, [End Page 309] pain reception, and emotion. The metaphysical goal is to identify a set of psychological properties possessed by all and only persons. Moral personhood, by contrast, indicates individuals who possess properties or capacities such as moral agency and moral motivation. Such properties or capacities distinguish moral persons from all nonmoral entities. In principle, an entity could satisfy all the properties requisite for metaphysical personhood and lack all the properties requisite for moral personhood.

However, most published theories of persons are not clearly distinguishable into these types or even attentive to the distinction between metaphysical and moral personhood. Proponents of these theories have generally not approached the subject through these distinctions. Their goal has primarily been to delineate the distinctive properties of personhood--moral or nonmoral--that are necessary for and confer moral standing on an individual. For three decades, and arguably for several centuries, 2 the dominant trend in the literature on persons has been to delineate nonmoral, usually cognitive, properties of individuals in a metaphysical account, from which conclusions can be drawn about moral standing. A typical example is Michael Tooley's well known analysis moving from metaphysical premises to moral conclusions (1972, sec. 3):

What properties must something have in order to be a person, i.e., to have a serious right to life? The claim I wish to defend is this: An organism possesses a serious right to life only if it possesses the concept of a self as a continuing subject of experiences and other mental states, and believes that it is itself a continuing entity.

Tooley (1983, p. 51; cf. p. 35) explicitly observes that

[I]t seems advisable to treat the term 'person' as a purely descriptive term, rather than as one whose definition involves moral concepts. For this appears to be the way the term "person" is ordinarily construed. 3

In this account, "person" has purely descriptive content ("an entity that possesses either self-consciousness or rationality"), and the person-making properties in this metaphysical account endow their possessors with moral rights or other moral protections.

The belief persists in philosophy, religion, science, and popular culture that some special cognitive property or properties of persons like self-consciousness confers a unique moral standing and perhaps forms the exclusive basis of moral standing. 4 I believe, however, that no cognitive property or set of such properties confers moral standing and that metaphysical [End Page 310] personhood of this sort is not sufficient for either moral personhood or moral standing (though some conditions of metaphysical personhood may be necessary conditions of moral personhood). 5 I also believe that moral personhood is not the sole basis of moral standing. I will argue, then, that metaphysical personhood does not entail moral personhood or moral standing and that personhood of either type is not the only basis of moral standing.

The Concept of Metaphysical Personhood

The common sense concept of person is, roughly speaking, identical with the concept of human being. Human psychological properties also continue to play a pivotal role in philosophical controversies over personhood. However, there is no warrant for the assumption that only properties distinctive of membership in the human species count toward personhood or confer moral standing. Even if certain properties strongly correlated with membership in the human species qualify humans more readily than the members of other species, these properties are only contingently connected to being human. It just so happens, if it is so at all, that individuals possessing these properties are of a particular natural species. The properties could be possessed by members of nonhuman species or by entities outside the sphere of natural species such as computers, robots, and genetically manipulated species. 6

Fortunately, a metaphysical account of persons need have no reference to properties possessed only by humans. In the cognitivist theories mentioned previously (e.g., Tooley's), an entity is a person if and only if it possesses certain cognitive rather than singularly human properties. Cognitive conditions of metaphysical personhood similar to the following have been promoted by several classical and contemporary writers: 7 (1) self-consciousness (of oneself as existing over time); (2) capacity to act on reasons; (3) capacity to communicate with others by command of a language; (4) capacity to act freely; and (5) rationality.

These characteristics presumably distinguish persons from nonpersons irrespective of species, origin, or type. For example, it is an open question whether a robot, a computer, an ape, or God would qualify for metaphysical personhood. Methodologically, the properties of personhood are presumed to be determinable a priori by consulting our shared concept of person; a theory does not require empirical discovery. The only empirical question is whether an entity in fact satisfies the conceptual conditions. A classical example of this method is found in John Locke's (1975, 2.27.9; [End Page 311] see also 2.27.24-26) analysis of a person as a "thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing in different times and places." Locke pointed out that despite the close association between "man" and "person," the two concepts are distinct, a claim he defended by presenting cases to show that the same man need not be the same person.

Sometimes it is said by those who defend criteria resembling 1-5 that only one of these criteria must be satisfied for metaphysical personhood--for example, self-consciousness, rationality, or linguistic capacity. Other writers suggest that each condition must be satisfied; the five conditions are jointly necessary and sufficient. The typical view seems to be that some subset of these five conditions is both necessary and sufficient.

Problems in Theories of Metaphysical Personhood

These cognitive theories all fail to capture the depth of commitments embedded in the language of "person," and they sometimes promote deep confusion by moving from a purely metaphysical claim to a claim about either moral personhood or moral standing. By themselves these cognitive properties have no moral implications. Such implications occur only if an analysis assumes or incorporates an independent moral principle, such as "respect for persons." Such a principle, being independent of a metaphysical theory, would have to be defended independently (and given some suitable content).

To illustrate this point, suppose that some being is rational, acts purposively, and is self-conscious. How is moral personhood or any form of moral standing established by this fact? Do moral conclusions follow from the presence of these properties? An entity of this description need not be capable of moral agency or able to differentiate right from wrong; it may lack moral motives and all sense of accountability. It may perform no actions that we can judge morally. It might be a computer, a dangerous predator, or an evil demon. No matter how elevated our respect for this entity's cognitive capacities may be, these capacities will not amount to moral personhood (and certainly will not establish any form of moral standing). Capacities of language, rationality, self-consciousness, and the like simply lack an intrinsic connection to moral properties such as moral agency and moral motivation.

A property often cited in the metaphysical hunt, as we saw in Tooley's theory, is self-consciousness, that is, a conception of oneself as persisting through time and having a past and a future. If animals such as birds and [End Page 312] bears lack self-awareness and a sense of continuity over time, they lack personhood (see, e.g., Buchanan and Brock 1989, pp. 197-99; Harris 1985, pp. 9-10; Dworkin 1988, esp. Chapter 1). However, it is more assumed than demonstrated in these theories that nonhuman animals lack a relevant form of self-consciousness or its functional equivalent. The prima facie evidence of various types and degrees of animal self-awareness is so striking that the possibility of self-consciousness cannot be dismissed without careful study. Language-trained apes appear to make self-references, and many animals learn from the past and then use their knowledge to forge plans of action for hunting, stocking up reserve foods, and constructing dwellings (see Griffin 1992). These animals are aware of their bodies and their interests, and they unerringly distinguish those bodies and interests from the bodies and interests of others. In play and social life, they understand assigned functions and decide for themselves what roles to play. A few appear to recognize themselves from reflections in mirrors (cf. Gallup 1977; DeGrazia 1997, p. 302; Patterson and Gordon 1993; Miles 1993). There may, then, be reason to attribute at least elementary self-consciousness to these animals, and to think of this ability as admitting of degrees in the several criteria that might be used to analyze it.

One possible strategy to avoid this conclusion is to increase the demands built into the concept of self-consciousness. Harry Frankfurt's (1971) well known account, sometimes presented as a theory of autonomy, could be adapted to this end (see also, Dworkin 1988, Chapters 1-4; Ekstrom 1993). In this theory, all and only persons have a form of self-consciousness involving distanced self-reflection. Persons reflectively judge and identify with their basic, first-order desires through second-order desires, judgment, and volition. Second-order mental states have first-order mental states as their intentional objects, and considered preferences are formed about first-order desires and beliefs. For example, a long-distance runner may have a first-order desire to run several hours a day, but also may have a higher-order desire to decrease the hours and the level of commitment. Action from the second-order desire is autonomous and is characteristic of the person; action from the first-order desire is not autonomous and is typical of animal behavior. The capacity to rationally accept or repudiate lower-order desires or preferences--a lofty cognitive ability of distanced self-reflection--is the centerpiece of the theory.

However, several problems haunt this theory. First, there is nothing to prevent a reflective acceptance or repudiation at the second level from being caused by and assured by the strength of a first-order desire. The [End Page 313] individual's acceptance of or identification with the first-order desire would then be no more than a causal result of the already formed structure of preferences, not a new structuring of preferences or a particularly attractive criterion of personhood. Second-order desires would not be significantly different from or causally independent of first-order desires (other than being second-order). To make this second-order theory plausible as an account of either autonomy or personhood, a component theory would have to be added that distinguished influences or desires that robbed an individual of autonomy or personhood from influences or desires consistent with autonomy or personhood.

Second, the conditions of distance and reflective control are so demanding in this theory that either many human actors will be excluded as persons or their actions will be judged nonautonomous. An identification at the second level is doubtfully present in most of the actions that we perform most of the time. A potential moral price of this demanding theory is that individuals who have not reflected on their desires and preferences at a higher level deserve no respect for actions that derive from their most deep-seated desires and preferences. The more demanding the conditions in a theory, the more it will encounter this problem and the more difficult it will become to interpret the scope and demands of moral principles such as respect for persons and respect for autonomy. 8

As the quality or level of required cognitive activity is reduced in a theory to accommodate these problems, the volume of humans who qualify will increase, but so will the volume of nonhuman animals. Less demanding conditions--understanding and self-control, say--will likely be satisfied to a greater or lesser extent. A threshold line therefore will have to be drawn in a theory that separates an adequate degree of understanding and self-control from an inadequate degree. Once again, a high threshold will exclude many humans that we normally regard as autonomous persons; a low threshold will include at least some nonhuman animals along with them.

Virtually all criteria of personhood or autonomy admit of degrees, and most develop over time. Rationality and understanding clearly admit of degrees (though self-consciousness is a more challenging case). A theory that embraces such degrees of autonomy--and perhaps thereby degrees of personhood--must allow for the possibility that some nonhuman animals will be positioned at a higher level of autonomy (or personhood) than some humans. 9 The fact that humans will generally score higher under these criteria than other species of animals is a contingent fact, not a [End Page 314] necessary truth about the human species. A nonhuman animal may overtake a human whenever the human loses a sufficient measure of cognitive abilities after a cataclysmic event or a gradual decline of capacity. If, for example, the primate in training in a language laboratory exceeds the deteriorating Alzheimer's patient on the relevant scale of cognitive capacities, the primate gains a higher degree of personhood, and may gain a higher moral standing. However, as noted earlier, metaphysical theories of persons that appeal exclusively to cognitive criteria entail no such conclusions about either moral persons or moral standing, two topics to which I now turn.

The Concept of Moral Personhood

By comparison to metaphysical personhood, moral personhood is relatively uncomplicated. I will not attempt an account of the necessary and sufficient conditions of moral personhood, but it seems safe to assume that a creature is a moral person if: (1) it is capable of making moral judgments about the rightness and wrongness of actions; and (2) it has motives that can be judged morally. These are moral-capacity criteria and also cognitive criteria, but they are not sufficient conditions of morally correct action or character; an individual could be immoral and still qualify for moral personhood. These criteria will require for their explication some of the cognitive conditions discussed previously. For example, the capacity to make moral judgments may require rationality. A general theory of moral personhood, then, would be needed to defend the above two conditions and to relate them to the cognitive conditions discussed

However, such a general theory is not needed for the two primary theses that I will defend. The first thesis is that moral personhood, unlike (cognitivist theories of) metaphysical personhood, is sufficient for moral standing. Moral agents are paradigm bearers of moral standing. Any entity qualifying for moral personhood is a member of the moral community and qualifies for its benefits, burdens, protections, and punishments. Moral persons understand moral reciprocity and the communal expectation that they will treat others as moral persons. It is central to the institution of morality itself that moral persons deserve respect and are to be judged as moral agents. Moral persons know that we can condemn their motives and actions, blame them for irresponsible actions, and punish them for immoral behavior. The moral protections afforded by this community may be extended to the weak and vulnerable who fail to qualify as moral [End Page 315] persons, but moral standing for these individuals must rest on some basis other than moral personhood.

The second thesis is that nonhuman animals are not plausible candidates for moral personhood, though the great apes, dolphins, and other animals with similar properties could turn out to be exceptions. 10 Here I borrow from Charles Darwin's The Descent of Man (1981, Chapter 3). He denies that animals make moral judgments, while affirming that they sometimes display moral emotions and dispositions. For example, he maintains that animals do not make genuine judgments of blame when they punish their peers for misbehavior, but that they do display love, affection, and generosity. Darwin described conscience (the moral sense in humans) as "the most noble of all the attributes" found in the human animal: "I fully subscribe to the judgment of those writers who maintain that of all the differences between man and the lower animals, the moral sense or conscience is by far the most important." Darwin thus thought of nonhuman animals as failing the test of moral personhood. 11

Humans too fail to qualify as moral persons if they lack one or more of the conditions of moral personhood. If moral personhood were the sole basis of moral rights (a view I do not hold), then these humans would lack rights--and precisely for the reasons that nonhuman animals would. Unprotected humans would presumably include fetuses, newborns, psychopaths, severely brain-damaged patients, and various dementia patients. I will now argue that these individuals do have some rights and merit moral protections, but not on the basis of moral personhood. In this respect, these humans are in the same situation as many nonhumans: Moral standing for them is not grounded in moral personhood any more than it is grounded in metaphysical personhood.

Moral Standing in the Absence of Personhood

It is fortunate for animals and humans who lack moral personhood that moral standing does not require personhood of any type. Some creatures have moral standing even though they do not possess even a single cognitive or moral capacity. The reason is that certain noncognitive and nonmoral properties are sufficient to confer a measure of moral standing.

At least two kinds of properties qualify a creature: properties of having the capacity for pain and suffering, and properties of emotional deprivation. As Jeremy Bentham pointed out, the capacity to feel pain and undergo suffering is more relevant to moral standing for nonhuman animals than are cognitive properties. 12 The emotional lives of animals, though seldom [End Page 316] discussed until very recently, are no less important. Animals experience love, joy, anger, fear, shame, loneliness, and a broad range of emotions that can be radically altered, distorted, or numbed by their circumstances (Griffin 1976; Orlans et al. 1998; Masson and McCarthy1995).

Nonpersons have many interests in avoidance of pain, suffering, and emotional deprivation. In principle the standing of such an individual could be so morally considerable as to outweigh certain moral rights and interests of persons. For example, the interests of animals could override the (qualified) rights of humans to do research, own zoos, run museums, and operate farms.

The injunction to avoid causing suffering, emotional deprivation, and many other forms of harm is as well established as any principle of morality. This injunction is fashioned to protect individuals because harm is bad in itself, not because it is bad for members of a certain species or type of individual, and not because the individual is or is not a moral person. Animals have interests in avoiding harms other than those of pain, suffering, and emotional deprivation. For example, they have interests in not being deprived of freedom of movement and in continued life. The range of their interests is beyond the scope of my arguments. I have merely maintained that we have at least some obligations to animals in complete independence of their status as persons and that noncognitive, nonmoral properties that confer moral standing form the basis of the obligation. This conclusion holds equally for humans lacking metaphysical and moral personhood.

Which Animals Have Rights?

Thus far I have not discussed whether moral standing includes rights for animals other than the human animal. In a well known article, Carl Cohen maintains that a right is a claim that one party may validly exercise against another and that claiming occurs only within a community. He argues that rights "are necessarily human; their possessors are persons" with the ability to make moral judgments and exercise moral claims. Animals cannot have rights, he says, because they lack these abilities (Cohen 1986, p. 865; 1990). That is, in my terminology, they lack moral personhood.

Though widely embraced, this view endangers animals and humans alike. A better account is that both humans and animals can be rights holders regardless of whether they are metaphysical or moral persons. This conclusion follows from my arguments about the diverse bases of [End Page 317] moral obligations, but those arguments need now to be combined with the widely accepted doctrine in law and morals that rights are correlative to obligations. On this account, obligations always imply corresponding rights if they are bona fide moral obligations (not merely self-assumed obligations or personal moral ideals, such as "obligations" of charitable giving for the arts). 13 "X has a right to do or to have Y" therefore means that the moral system of rules (or the legal system, if appropriate) imposes an obligation on someone to act or to refrain from acting so that X is enabled to do or have Y. The language of rights is always translatable in this way into the language of obligations. For example, if a research investigator has obligations to animal subjects to feed them and abstain from extremely painful procedures during the conduct of research, then animal subjects have a right to be fed and not to have the pain inflicted. Correlativity requires that anyone who recognizes obligations logically must recognize that animals have whatever moral rights correspond. Since Cohen and most thoughtful persons believe in some range of human obligations to nonhuman animals that derive from some source, it follows that the animals have correlative rights.

Possession of a right is also independent of being in a position to assert the right. A right-holder need not be the claimant in a particular case. For example, small children and the mentally handicapped may not be able to understand or claim their rights. Nonetheless, they possess them, and claims can be made for them by appropriate representatives. Similarly, animals have all the rights correlative to obligations that humans owe them, and they have these rights regardless of whether they or any surrogate is in a position to exercise the rights.

Whatever the precise set of rights of animals and of humans who fall short of moral personhood (and whatever their precise level of moral standing), that set of rights will not be the same as the set of rights enjoyed by moral persons. Because bears and beagles lack the accountability and moral agency found in moral persons, their rights are different. A theory of moral personhood should help us understand why some entities have a full moral standing, but the theory will not be sufficiently powerful to exclude other entities from a partial moral standing. This point is not trivial, because some of the most important moral questions about our uses of both humans and nonhumans--for example, as sources of organs and as subjects of research--turn on the precise moral standing of these animals. [End Page 318]

The Problem of Vagueness in the Concept of Person

One final problem about theories of personhood deserves attention. Literature on the criteria of persons is mired in intractable dispute in a wide range of cases, including fetuses, newborns, the irreversibly comatose, God, extraterrestrials, and the great apes. Facts about these beings are not the source of the dispute. The problem is created by the vagueness and the inherently contestable nature of the ordinary language concept of person, 14 with its commitments to a human individual comprised of a rather open-textured set of mental traits.

The vagueness of this concept is not likely to be dissipated by general theories of personhood unless they are revisionary. Theories typically reflect the concept's vagueness and kindle more disagreement than enlightenment. 15 They give us no more than grounds for a claim that there are alternative sets of sufficient conditions of personhood. The possibility of necessary and sufficient conditions of person in a unified theory now seems dim. The concept of person is simply not orderly, precise, or systematic in a way that supports one general philosophical theory to the exclusion of another.

There is one obvious solution to this problem of vagueness in the concept of person: Erase it from normative analysis and replace it with more specific concepts and relevant properties. I favor this option for both metaphysical personhood and moral personhood because it would enable us to go directly to the heart of substantive moral issues instead of using the oblique detour now made through theories of personhood. That is, we could inquire directly about the moral implications of possessing specific nonmoral and moral properties, such as reason and moral motivation, or we could discuss the substantive bases of ascriptions of rights. Questions about whether fetuses can be aborted, whether xenotransplantation is permissible, and whether anencephalics can be used in human experiments would then be recast in terms of whether and, if so, on what moral grounds such actions can be performed.

This suggestion should not be taken to imply that we should abandon philosophical theories of metaphysical persons and moral persons. My interest is exclusively in eliminating the abuse of these theories in normative analysis, not in eliminating the theories themselves. [End Page 319]


I have said relatively little about specific normative problems or about the practical implications of the conclusions I have reached, but not because these questions are unimportant. I conclude with a comment on how very important they are.

Much has been made of the potential breakdown of the lines that have traditionally distinguished human and nonhuman animals. If nonhumans turn out to possess significantly more advanced capacities than customarily envisioned, their moral standing would be upgraded to a more human level. However, this possibility remains speculative and may be less important than the thesis that because many human lack properties of personhood or are less than full persons, they are thereby rendered equal or inferior in moral standing to some nonhumans. If this conclusion is defensible, we will need to rethink our traditional view that these unlucky humans cannot be treated in the ways we treat relevantly similar nonhumans. For example, they might be aggressively used as human research subjects and sources of organs.

Perhaps we can find some justification of our traditional practices other than a justification based on status as person or nonpersons. However, if we cannot find a compelling alternative justification, we either should not be using animals as we do, or we should be using humans as we do not. 16

Tom L. Beauchamp, Ph.D., is a Senior Research Scholar at the Kennedy Institute of Ethics and Professor of Philosophy, Georgetown University, Washington, DC.


1. Other philosophers have used this or a similar distinction, but not as I analyze the distinction (cf. Dennett 1976, esp. pp. 176-78; Feinberg and Levenbook 1993; Sapontzis 1987, pp. 47ff.).

2. A respectable case can be made that Aristotle, Boethius, Descartes, Locke, Hume, and Kant either presupposed or argued for this position. However, Kant's apparent inclusion of moral autonomy renders him a borderline case, and other qualifications would need to be made for some of these figures.

3. Tooley's clarification of the distinction between the descriptive and the normative functions of "person" is useful. For a concise and persuasive account of the descriptive (factual) and normative (implying rights and duties) uses of the concept of person and the philosophical importance of the distinction, see Biernbacher (1996, p. 143). However, neither account captures the notion of moral personhood, which is more descriptive than normative. The normative dimension is best understood in terms of the moral standing of persons, irrespective of whether that standing is attributed on the basis of metaphysical or moral personhood. This point seems generally overlooked in the relevant literature (see, e.g., Gervais 1986. p. 181).

4. Throughout the histories of philosophy and law, there has been little resistance to the postulate that animals have no moral or legal standing because they lack the properties that confer standing. Animals have been given almost no legal standing in British and American systems of law, but questions of their moral standing are far from decided (see Frey 1988, esp. pp. 196-97; Rachels 1990; Beauchamp 1992; Regan 1983; Francione 1995, Chapter 4; DeGrazia 1997).

5. I do not deny the possibility of a theory of metaphysical personhood. My objections do not apply to some of the early and influential metaphysical accounts in contemporary philosophy, such as Strawson (1959) and Puccetti (1969). Locke, as cited earlier, is another example.

6. On the relevance and plausibility of robots and physical-mental systems that imitate human traits, see Pollock (1989) and Marras (1993).

7. See Tooley (1972; 1983); also see Tooley (1984); Warren (1973, esp. sec. 2; 1991, esp. pp. 310-13); Engelhardt (1996, Chapters 4, 6); Lomasky (1987). See too the articles and bibliography in Goodman (1988).

8. There are more demanding theories than these second-order reflection theories. Some theories demand that the autonomous individual be authentic, consistent, independent, in command, resistant to control by authorities, and the original source of values, beliefs, rational desires, and life plans (see Benn 1976; 1988, pp. 3-6, 155f, 175-83; see also Savulescu 1994).

9. Some measure of personhood is gained or lost over time as critical capacities are gained or lost, feeding the hypothesis of degrees of personhood.

10. For the kinds of capacities and action that appear to constitute an exception, see the study of gorillas in Patterson and Gordon (1993, esp. pp. 70-71).

11. Darwin argues that moral sensitivity is itself the product of evolution. He maintains thought that some humans display a high level and other humans a low level of moral responsiveness; the highest level of morality is reached when persons extend their sympathies beyond their own group and indeed beyond their own species to all sentient creatures.

12. Bentham (1948, Chapter 17, sec. 1) reasons as follows: "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. . . . But is there any reason why we should be suffered to torment them? Not any that I can see." In recent extension, Donald Griffin has argued that no good reason exists to place a special weight on the distinction between perceptual awareness in animals and a reflective consciousness. Griffin (1992, esp. p. 248) proposes multiple levels of mentation shared across species, from basic pain receptors to intentionality (see also Rodd 1990; DeGrazia 1996).

13. See Joel Feinberg's (1989) argument that animals can have rights because they have, or at least can have, interests that we are obligated to protect.

14. For an early and influential analysis of this problem, see English (1975); see also, DeGrazia (1996, esp. pp. 305-15).

15. Some theories appeal to human characteristics, others to beings with moral standing, others to those with properties such as second-order volition (Frankfurt), moral volition (Kant), and the capacity to experience pain and suffering (Bentham). Each account is tied to some larger philosophical doctrine. Without judging the merits of the latter, it is difficult if not impossible to judge the former.

16. This conclusion has been influenced by private discussions with Raymond Frey (see Frey 1996; see also the engaging essay by Rachels 1993).


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