Abstract The prospect of creating and using human–animal chimeras and hybrids (HACHs) that are significantly human-like in their composition, phenotype, cognition, or behavior meets with divergent moral judgments: on the one side, it is claimed that such beings might be candidates for human-analogous rights to protection and care; on the other side, it is supposed that their existence might disturb fundamental natural and social orders. This paper tries to show that both positions are paradoxically intertwined: they rely on two kinds of species arguments, “individual species arguments” and “group species arguments,” which formulate opposing demands but are conceptually interdependent. As a consequence, the existence of HACHs may challenge exactly those normative standards on which the protection of HACHs may eventually be based. This ethical paradox could constitute the ultimate source of the “moral confusion” that some authors have suspected HACHs to provoke. chimeras, ethical paradox, human–animal mixtures, hybrids, moral confusion, species arguments I. INTRODUCTION The creation and use of human–animal chimeras and hybrids (henceforth: HACHs) has become an intensively discussed topic in recent bioethics. The current debate is shaped by a multitude of different positions concerning the moral status of HACHs and the normative appraisal of their production and application in research and therapy (for an overview, see Baylis, 2008; Badura-Lotter and Düwell, 2009; Hug, 2009). In this paper, I highlight a peculiar constellation of ethical arguments concerning HACHs that may account for some specific perplexity with regard to their moral evaluation. More precisely, I will argue that HACHs engender a paradoxical interplay of individual species arguments (ISAs) and group species arguments (GSAs), which leads to a conceptual impasse in their normative assessment. In doing so, my approach connects to a well-known work by Robert and Baylis that may be said to have initiated the current debate on HACHs. A central point of their argument is that crossing species boundaries between humans and animals might conjure up an inexorable moral confusion: Human–animal mixtures, they claim, stand in between two groups with qualitatively different moral status; that is, human beings, enjoying their moral status independent of other people’s wishes and intentions (absolute, full moral status), and animals, whose moral status is at least partly contingent on the wills and attributions of human persons (relative, conditional moral status). Because of their middle position, HACHs tend to blur this highly important distinction. The resulting moral confusion within human society, in turn, might have precarious effects on various levels of human interaction (Robert and Baylis, 2003, 9–10). Robert and Baylis’ argument has been criticized for a variety of reasons. Inter alia, it has been observed that it relies heavily on consequentialist thinking. The consequences envisaged, however, may be empirically uncertain and insufficiently substantiated (Streiffer, 2003, 37). The argument I want to develop in this paper is also based on the idea of some moral puzzlement induced by HACHs. However, I try to trace this moral disorientation back to an irreducible ethical dilemma: Human–animal mixtures, depending on their concrete set-up, may have considerable or even full moral status. At the same time, they tend to undermine the cogency of an essential type of argument that bestows that very status on them in the first place. I contend that this constellation is the ethical source of confusion that moral attitudes toward HACHs may indeed display. Note that this outlook is not empirical or consequentialist in nature. It does not envision the erosion of central common norms and subsequent negative effects on society. Rather, it refers to conceptual problems underlying the relevant arguments. In the following, I will try to flesh out the moral bewilderment that the prospect of HACHs conjures up by outlining two deeply rooted but ultimately opposing moral intuitions concerning HACHs (Section II). To explicate their ethical background, I will elaborate on two pertinent arguments referring to HACHs’ creation and use; that is, ISAs (Sections III–IV) and GSAs (Sections V–VI). I will show that the relation between these arguments is paradoxical, because they are interdependent in their ethical foundations, while being contradictory in their moral implications (Section VII). After sketching related positions and discussing two objections (Sections VIII–IX), I will conclude by suggesting that the moral confusion HACHs are said to imply in fact mirrors the ethical cul-de-sac in which those two arguments are entangled (Section X). Before embarking on this project, I want to make two explicit disclaimers. They concern the aim and the scope of this paper and may help to prevent some premature reservations against its line of argument. First, I will not discuss the question of how to define the concept of species or of which definition of species to apply. There are different proposals in theoretical biology and evolutionary theory, as well as in philosophy of biology, and the debate is still ongoing (see Austriaco, 2006, 67–71; Cobbe and Wilson, 2010, 180–5). Some authors even reject the concept of species altogether as ontologically untenable or at least as morally irrelevant (see Robert and Baylis, 2003, 2–6; Karpowicz, Cohen, and van der Kooy, 2005, 117). I do not share the latter scepticism but rather suppose that the concept of species is indispensible, not least in order to give an ontological definition of chimeras and hybrids (as beings with biological material from different species) and to assess their moral status (based on that definition). Note that this position does not stipulate any kind of realism, let alone essentialism concerning biological species. It may well take a nominalist and merely regulative outlook by regarding biological species as a necessary and nonarbitrary classificatory concept for scientific research and ethical evaluation. I certainly agree that the arguments developed in what follows may vary in their impact, depending on which species concept is applied, and possibly they favor one definition over the other. However, these questions are not the concern of this paper. Second, I will not endeavor to elaborate which kinds of HACHs might actually prove problematic in view of the argument I present. Clearly, not all human–animal mixtures are adequate targets of criticism. The prevalent positions in the bioethical debate vary widely with regard to the types of HACHs whose creation and use they regard as objectionable. Similarly, the paradoxical intertwinement of ISAs and GSAs that I try to unfold in this paper will only be conjured up by certain kinds of HACHs. It is not my purpose here to investigate in more detail which HACHs actually have this disturbing effect. This paper is supposed to outline a general structure of arguments, not to anticipate details of their concrete application. Correspondingly, I will restrict myself to formulations like “sufficiently human,” or “relevantly human-like,” in order to address HACHs that stand effectively between human beings and animals and thus may have the antinomical implications I want to carve out. In order to focus his intuitions, the reader may consider a concrete case that would arguably be worrisome in light of the arguments I will present, for example, a humanzee with a considerably human-like brain, a potential for interbreeding with human beings, a halfway-human-like appearance and close-to-human abilities such as rudimentary language use and a basic understanding of abstract concepts. II. THE MORAL QUANDARY OF HACHS The prospect of generating and utilizing HACHs, particularly if they were to display a sufficiently human component in their biological make-up, their general appearance, their cognition or behavior, seems to evoke strong intuitive reservations. Correspondingly, there is a basic consensus in many expert opinions and recommendations that HACH projects should be assessed with peculiar scrutiny or possibly dismissed altogether, particularly when the mixing of human and animal material extends to such delicate areas as the brain or the germ-line, or when higher animals such as great apes are involved (ISSCR, 2007; Scottish Council on Human Bioethics, 2010; Academy of Medical Sciences, 2011). A closer look reveals that, curiously, moral intuitions concerning relevantly human-like HACHs seem to point in opposite directions. On the one hand, there is a strong presumption that such beings deserve special protection, possibly to a higher degree than unmodified animals, by virtue of their human portions: they should be spared damage and exploitation, and they may even be entitled to an adequate environment and targeted support to allow for a proper development of their respective capabilities. On the other hand, the idea of such beings arouses serious feelings of rejection, suggesting that they would establish something utterly wrong in the natural and/or social order: they should not exist, thus not be created in the first place, and if they come into being they should preferably be terminated, ideally at some early point in their development. One might object that these opposing intuitions are not contradictory in a strict sense: one may disapprove of a HACH being brought into existence and still hold that it requires adequate treatment once it is created. Yet, this assessment does not fully appreciate the content of the two attitudes and their deeply divergent nature—a drive to protect or even support a HACH, and an intuition that it disturbs some essential order. This is particularly true because the latter intuition commits one not only to the wish that a HACH should be prevented from coming into existence, but also, as will become more tangible in what follows, to the prima facie conviction that a HACH should be eliminated once it was created—which is in clear contradiction to its supposed entitlement to protection and support. One might suggest that the two intuitions simply represent dissenting attitudes toward HACHs, that is, attitudes that only different persons, or at most one and the same person at different times, will take: some people regard HACHs as worthy of protection and support, others reject, fear, or despise them. There is nothing particularly remarkable about such disagreement, one might object. Hence its analysis will reveal nothing but opposing standpoints, a familiar situation in other bioethical fields such as embryo protection or stem cell research. However, it is certainly conceivable that the two attitudes—finding a HACH worthy of protection and repudiating its existence—may be encountered within one person at the same time. This ambiguity may unfold in emotional reactions that rest uneasily between pity and repulsion, fascination and abhorrence, resisting any simple resolution toward either side. Finally, one might want to explain this possibility of judgmental dissonance by the fact that moral convictions often prove to be inconsistent when analyzed in more detail: people’s normative positions are notoriously mixed and fragile, moral intuitions, particularly when they concern new situations or novel entities, are regularly unstable and frequently self-defeating. One might conclude that, correspondingly, there is nothing to gain from analyzing contradictory attitudes toward HACHs, even if they occur within the same person at the same time, because such perplexity conveys no relevant meaning or truth. Yet, I want to argue that this particular ambiguity toward HACHs—considering them worthy of moral respect while simultaneously resenting their actual presence—has a deeper, nonarbitrary foundation. Sometimes moral disorientation or indecision is a hint toward substantial ethical problems, or even antinomical structures. To bring those to light may be helpful in grasping a given practice in its normative complexity. To unearth these ethical problems behind the moral quandary surrounding HACHs, I will sketch two central arguments that may demand a HACH’s protection or call for a HACH’s destruction, respectively. Both arguments are “species arguments”—which may not be surprising while discussing entities produced by crossing species boundaries. However, these “species arguments” are very distinct with respect to their normative foundations and their central objects, one focussing on the moral status of individuals, the other concerning the moral integrity of groups. Furthermore, their ethical relationship is slightly paradoxical, because they contradict each other in their concrete application to HACHs while presupposing each other in their basic demands and justifications—which may prove to be the ultimate source of the moral confusion that HACHs are said to conjure up. III. ETHICAL ARGUMENTS FOR THE PROTECTION OF HACHs Many authors stress that certain types of HACHs, once created, might be candidates for special requirements concerning their adequate treatment. Particularly, one suggestion is that some HACHs may be eligible for special protection against harm and instrumentalization, or even for suitable support regarding the development of their capabilities. Central issues in these debates are the moral status of the new organism (especially whether it is to be regarded as an animal-like being or as a human-like being) and the normative standards that derive from this status (e.g., physical and psychological welfare of a sentient being, specific dignity of a rational and/or moral being). Arguments advanced closely relate to debates on the moral status of other biological entities that may be worthy of special protection and care, such as higher vertebrates, great apes, but also human embryos, or the mentally disabled. First, capacity arguments refer to the presumed faculties of a HACH, more precisely not to the actual exercise of these faculties, but to their basic presence within that being. Sentience, particularly the capacity to experience bodily and mental pleasure and pain, would introduce the norms of not violating and of safeguarding physical and psychological welfare, as exemplified in common animal ethics, for example, in the triple standard of reduction, replacement, and refinement. Higher cognitive capacities, particularly rationality and morality, would give rise to additional norms of noninstrumentalization or respect for dignity, applying to all autonomous beings and finding expression in specific rules such as nonutilization for external purposes or observance of informed consent. A substantial number of ethical commentators on HACH experiments and practice emphasize this possible human-analogous status of certain higher HACHs, particularly human–animal brain chimeras, and the moral consequences that would result from such a status (Glenn, 2003, 27–8; Savulescu, 2003, 24; DiSilvestro, 2004, 16–22; Karpowicz, Cohen, and van der Kooy, 2004, 333–4; Kopinski, 2004, 654–55, 662; Karpowicz, Cohen, and van der Kooy, 2005, 123; Streiffer, 2005, 348, 362–3; Austriaco, 2006, 71; Mirkes, 2006, 116, 126–7; Seyfer, 2006, 48; DeGrazia, 2007, 326; Benham and Haber, 2008, 43; de Melo-Martin, 2008, 338–9; Badura-Lotter and Düwell, 2009, 197–8; Eberl and Ballard, 2009, 477, 480; Streiffer, 2010, 240, 244; Haber and Benham, 2012, 22–3; Piotrowska, 2014, 7–11). Also, frequently noted is that the prospective settings of research and application would hardly allow for the kind of treatment that these norms demand: The HACH would most probably be harmed or killed; it would definitely be instrumentalized without consenting, due to the very purpose of its creation, that is, the performance of a scientific experiment or the retrieval of biological material. If, correspondingly, these norms cannot be fulfilled, one should rather abstain from generating the HACH in the first place. Alternatively, one might consider early termination, the insertion of “terminator sequences” into the HACH’s genome (by way of altered nuclear transfer, ANT), or the creation of HACHs that are inherently unable to develop beyond very early stages (such as human–animal cytoplasmatic hybrids, “cybrids”). These measures would ensure that the putative capacities conferring moral status on a HACH do not obtain. Correspondingly, harming or using the HACH during research and application would remain unproblematic, because there was no being involved with features barring these practices. The latter solutions become dubious, however, when moral status is not based on actual capacities but on the potential to develop such capacities. Potentiality arguments are familiar from debates on embryo protection, claiming that the active potential of an early organism to develop into an autonomous being, as opposed to the mere logical possibility of this development, bestows essential rights on this organism, particularly the rights not to be destroyed or instrumentalized. This line of argument may well apply to early HACHs when they have the active potential to develop into a being capable of rational and/or moral thought and behavior. Correspondingly, some authors consider even early HACHs to have a relevant moral status, claiming similar rights to protection and nonutilization, as are often attributed to human embryos (DiSilvestro, 2004, 17; Mirkes, 2006, 116, 119, 126; Seyfer, 2006, 48; Eberl, 2007, 54; Eberl and Ballard, 2009, 480–1). From that standpoint, at least some of the above “solutions” to problems arising from the status of HACHs are no longer eligible: Early termination is excluded by the very idea of a potentiality argument because it attributes rights against destruction, just like against any other harm or utilization, already to the early organism, simply because of its developmental potential. Insertion of “terminator sequences” via ANT would, arguably, be no better, for although the ensuing HACH would carry the killing process within its own biological setup, this lethal component would be the result of an additional intervention. Accordingly, it should be regarded as some deliberate damage done to the HACH, straightforwardly conflicting with its basic right to protection, as established by its original potentiality, rather than justifying any subsequent harm or utilization, ostensibly warranted by its destroyed potentiality. (Similarly, human embryos incapable of development due to ANT are scarcely regarded as an exemption from embryo protection based on potentiality arguments, but in fact as a clear violation of just that protection.) A human–animal cybrid might actually be different because its lack of developmental potential is not due to some extra intrusion but is a feature of its essential make-up. Consequently, the cybrid never falls under a potentiality argument that might bestow any rights on it. This is probably the main reason why the use of human–animal cybrids has met little resistance in ethical discussions of HACHs. Finally, there is another type of argument that may be used to establish that some HACHs have significant moral status. Again, this argument is well known from debates on human embryo protection. Similar to the rights of human embryos a HACH’s protective rights may be founded on species arguments. According to these, a particular organism is to be protected against harm and utilization, as long as it belongs to a biological lineage whose members are normally capable of rational deliberation and/or moral insight. This protection is independent of an organism’s individual capacities or potentialities. It only refers to its belonging to a rational and/or moral species. Again, this argument extends to early stages of an organism and prohibits any practices that may harm or use it or deprive it of its developmental options: Early termination of a member of a rational and/or moral HACH species, just like any other damage or instrumentalization, is inadmissible, due to the very meaning of a species argument. Applying ANT to prevent a HACH from unfolding into a fully developed organism would hardly alter its species membership from which its rights against damage and instrumentalization, and not least against this very intervention itself, derive. Even the creation and application of human–animal cybrids might turn out to be problematic, if their high proportion of human genes (over 99%) was regarded as an indicator of their actual (or virtual) belonging to the human species, qualifying them for corresponding rights against harm and use, regardless of their inherent lack of developmental potential (Badura-Lotter and Düwell, 2009, 199, 206; Jones, 2011, 90–1, 110–1). All three types of arguments, capacity, potentiality, and species arguments, focus on the moral status of HACHs. Referring to that status, they either require proper treatment of a HACH or, if that cannot be reasonably guaranteed, demand that we abstain from its very creation (possibly allowing for early termination, for induced inability to develop or for entities inherently incapable of development). By contrast, the mere existence of a HACH as such poses no problem for either argument. All they prescribe in this case is that this being is adequately handled (provided that its bringing into existence is not in itself considered an act of harming or instrumentalizing and, thus, as a form of maltreatment). In the following, I focus on the logic of species arguments. Admittedly, these are not openly endorsed by a majority of commentators on HACH research and application. Most work in this area, in fact, is more or less explicitly concerned with capacity reasoning. It concentrates on the sentience and cognition that full-grown HACHs might display and attributes protective rights to them accordingly. A few authors extend their arguments to early developmental stages, thus hinting at some implicit potentiality reasoning. Only rare remarks point in the direction of species membership as a source of moral status for HACHs. Still, I suggest that species arguments deserve closer attention, for several reasons. First, HACHs are simply defined as beings with biological material from different species. It is at least worth exploring whether their moral status might be closely linked to this essential feature. Second, it is not surprising that at a comparably early stage of discussion the attention focuses on the normative standing of a fully developed HACH in order to obtain a first grasp of its moral status. Nevertheless, this does not preclude further investigation to reveal that potential development or species membership are also relevant. Third, advanced debates in other biomedical fields arguably demonstrate that corresponding expansions may be reasonable. In particular, the comprehensible attitude of ascribing full moral status to human new-borns is preferably based on potentiality arguments, while the equally intelligible demand to grant full moral protection to severely mentally disabled people must eventually rely on species arguments. Finally, as I will try to show, it is the latter that may provide an explanation for the above-mentioned moral ambiguity in the appraisal of HACHs. To be sure, exactly this moral ambiguity may eventually convince one to abstain from a species perspective. Even then, however, exploring that perspective is still an illuminating enterprise and philosophically desirable in order to better understand its ethical texture. IV. DISTINCTIONS AND RECTIFICATIONS It is important to note that species arguments do not amount to speciesism. Speciesism entails favoring members of a particular species (usually one’s own) which is selected without naming any objective merits of that biological group. It is thus a form of partiality, analogous to racism or sexism, differentiating between beings not with respect to certain general properties with definite moral weight, but only with regard to their individual affiliation to some arbitrary group—that is, without providing relevant reasons for that distinction.1 A species argument, by contrast, attributes rights of protection to members of any species whose representatives usually display specific significant capacities—particularly capacities of rational and/or moral behavior, of reason and/or autonomy. This is no form of partiality at all, but a reproducible nonarbitrary distinction on the basis of important general traits. The general feature regarded as conferring moral status is a being’s membership in any rational and/or moral species (for a very clear account, see Jones, 2011, 103–6).2 A majority of thinkers appear to suppose that human beings constitute the only species presently known to have the relevant properties of rationality and/or morality. If this is correct, only human beings fall in the range of species arguments—which is the usual conceptual background of bioethical positions commonly termed “anthropocentric.” However, if it should turn out that members of any other species, presently known or unknown, currently existent or nonexistent, generally exhibit similar capacities of rational and/or moral behavior, a species argument would straightforwardly embrace all its representatives in an analogous way. It would protect its full-grown healthy members as well as its infants, embryos, disabled, and demented—demonstrating that its core rationale is actually “logocentric” rather than “anthropocentric” in the first place.3 Thus, species arguments can easily be defended against the formal accusation of being speciesist. Still, the arguments have to answer two questions regarding their specific content, the first being why rationality and/or morality should be good candidates for basing protective rights on them. The most common strand of reasoning claims, in line with a Kantian perspective, that beings holding these properties are able to set themselves goals. Consequently, it is not appropriate to use them as mere means to someone else’s ends, which establishes their right not to be instrumentalized. Rights protecting rational and/or moral individuals from being involuntarily harmed, impaired, aggrieved, killed, etc., can be connected to this argument: either they may be designed as special cases of noninstrumentalization, or they may be founded on a being’s living or sentient nature and then reinforced in their normative relevance by the standard of noninstrumentalization. The latter option, in particular, highlights the fact that basing certain protective rights on rationality and/or morality need not amount to denying nonrational/nonmoral beings protective rights of any other kind: living and sentient beings, with regard to these features, may be attributed rights to protection from harm and killing, but they will not, in virtue of these rights, have to be protected against instrumentalization.4 One may agree that rational and/or moral beings have a special moral status and still dispute the cogency of species arguments. For, the second question is why moral status should be accorded to all members of a rational and/or moral species, rather than only to those who actually have these capacities. The basic idea behind this extension can be best understood by referring to the tradition of human rights thinking. It seems essential to the logic and endorsement of human rights that no living member of the human race needs to pass any kind of “acceptance test” before these rights are assigned to him or her. Even though they are based on certain capacities that healthy adult human beings usually display, such as rationality and/or morality, nobody is required to demonstrate his or her individual level of competence before being declared eligible for a corresponding level of protection. It seems obvious that the notion of such an “acceptance test” would be highly precarious. First, in a pragmatic sense, it would encourage all sorts of discriminatory practices: it would be all too easy to manipulate application standards and test procedures in order to exclude undesired individuals or groups (presumably, it would be impossible to attain consensus on any definite canon of test criteria in the first place). Second, and more importantly, from a systematic perspective such a test contradicts the very idea of human rights: human rights are meant to establish a protective realm that includes beings in virtue of their most elementary constitution, rather than to introduce a privileged class for which anyone must qualify through critically examined performances (a highly appreciable account of this position, although prematurely concluding that animals can have no rights at all, is provided by Cohen, 2001, 37). According to this viewpoint, a human being unable to display certain capacities is not to be denied access to humanity’s protective realm. On the contrary, he or she ought to be regarded as a disadvantaged member of that realm, possibly ill or disabled, definitely in need of help, whose claims to corresponding protection are presumably even more urgent than those of other human beings.5 This unconditional extension of human rights to all human beings, regardless of their individual level of proficiency in any cognitive engagement or intellectual technique, has been an essential step to their comprehensive acknowledgement. It has functioned as a core element of fighting discriminatory practices like racism and sexism (rather than promoting such discrimination, as might be suggested by opponents to species arguments). It establishes a global community of beings that may base their self-conception on certain distinctive capacities but that are supposed to accept and acknowledge each other with no regard to their individual achievements concerning these capacities. It constitutes an all-embracing union of members sharing a certain biological nature which usually implies the presence of rational and/or moral features, without requiring anyone to demonstrate his or her mastery of those features before he or she be admitted. Species arguments rely on that very same logic of an inclusive, nonrestricted community, and apply it to biomedical issues. If individual levels of culture or education have no import, in line with the above argument, then neither do age or mental constitution (again as a matter of nondiscrimination, rather than of discrimination). Any human being, whether an adult, new-born, demented, or disabled, belongs to that union of mutual support and protection. No human being has to apply for admission, no human being needs to pass an individual test concerning his or her rational and/or moral faculties in order to be granted membership. It is characteristic of species arguments, in contrast to capacity and potentiality arguments, that they preserve that emphatic appeal to an inalienable affiliation with a protecting group, which is found in political discourses on human rights. All they do is transfer this emphasis from the classical dimensions of ethnicity, gender, culture, and education to the biological dimensions of developmental stages and possible impairments.6 It is worth emphasizing that species arguments, by their very meaning, refer to membership in a biological group, not just to belonging to some abstract category. So it would not be in line with a species argument, for instance, to declare that all “rational animals,” by definition, belong to the “human species” (as has been suggested by Oderberg, 2014, 211–3, 215f, 219–21, 224f), and thus deserve the same level of protection. “Rational animal” is not a biological species, but an abstract type, as referred to, for example, by capacity or potentiality arguments. Consequently, belonging to such a type would still be a matter of individual proof, that is, of demonstrating that some individual has the features or prospects in question before assigning it to that type. A species argument, by contrast, relies on membership in some biological group, whose representatives usually display those features or prospects, but which in itself is defined by independent, natural properties, such as the ability to interbreed or the sharing of a common ancestry. Such a biological group is supposed to establish a substantial connection in its own right, which can then be referred to by a species argument, thus sparing the individual any burden of proof concerning its capacities or potentialities. So, equating “rational animal” and “human species” may be an interesting move in other philosophical contexts (particularly in metaphysical classification). However, it undercuts exactly what a species argument proposes to do in biomedical ethics, that is, grounding protective rights on biological affiliation rather than on conceptual attribution. Further arguments would need to specify how strong rights against harm and instrumentalization based on this conception are in comparison to the “original rights” of human adults. Presumably, one will not concede any substantial weakening of these rights when talking about new-borns or demented people. However, killing a human embryo is probably not to be equated with killing a mentally disabled person, even if both acts may be qualified as wrong according to a species argument. At this point, actual capacities to experience fear or pain may figure in a more precise determination of rights based on a species account. HACHs may belong to a species whose members generally display the capacity for rational and/or moral behavior, hence applying species arguments to them in order to establish their protective rights is not missing the point. In fact, such arguments could be developed in two ways: First, a HACH may host a sufficient proportion of human material or structure in order to qualify as a member of the human species (such as a human–animal cybrid). Second, a certain type of HACH may itself be reckoned a new species with sufficient rational and/or moral capacities in order to extend a species argument to all its members (e.g., to all human–ape brain chimeras of a certain kind or lineage). V. ETHICAL ARGUMENTS AGAINST THE EXISTENCE OF HACHs Some ethical concerns about the generation of HACHs refer, loosely, to serious ontological problems and ensuing normative disruptions that the existence of such beings might entail. Allegedly, creatures that combine human and animal parts may undermine species integrity as well as human identity. In doing so, they violate relevant natural orders (marked by moral taboos, aesthetic repugnance, or religious reservations) or disturb essential social demarcations (eroding significant differences between humans and animals, respectively). Arguments in this line cling to the conceptual and moral significance of fixed species boundaries that are presumed to be blurred by the presence of HACHs, due to their mixed biological set-up. The exact ethical background of such concerns is not easily reconstructed: they are mentioned in many works, but mostly by people who more or less explicitly reject them. These authors either regard the production of HACHs as ethically unproblematic or turn to other arguments in order to criticize their creation. In fact, it is not easy to find academic sources actually endorsing these positions, which may nourish the suspicion that, occasionally, they serve as straw men in order to prepare one’s own truly “rational” or metaphysically “neutral” argument. This may seem particularly so when these positions are framed as accusations against scientists “playing God” or not respecting the “sanctity of the creation” (see Robert and Baylis, 2003, 7; Streiffer, 2005, 360; Baylis, 2008, 24). Regardless of these caveats, there are positions that insist on the ethical importance of fixed species boundaries: they appear in scholarly work, although their normative structure is not always unfolded unambiguously. To some extent, such views certainly prevail among the public and are possibly operative in intuitive reactions of immediate repulsion that the imagination of HACHs easily provokes (see Streiffer, 2005, 351–2). The concerns in question are present, for example, in claims that HACHs may constitute a threat to human dignity—not in the sense of a status argument, according to which HACHs might share in human dignity and should be respected accordingly (see Section III), but rather in the sense that the moral identity of the human species could be undermined by the existence of HACHs (Seyfer, 2006, 48–9; Jones, 2011, 107–10). Similar worries are expressed in suggestions that crossing species boundaries between human beings and animals violates species integrity—supposing that such integrity does constitute a morally relevant threshold for human action (Streiffer, 2003, 37). The rather vague reference to “moral taboos” that might be infringed by HACHs belongs, more often than not, to the same category of argument (see Seyfer, 2006, 49). Appeals to a “natural order” that needs to be respected and that HACHs ostensibly disturb are based on comparable convictions (see Streiffer, 2003, 38). In Sections VI and VII, I will try to give a more informative account of the ethical logic that seems to underlie these reservations against the existence of HACHs. For the time being, it shall suffice to reiterate that although these concerns refer to the integrity of the human species, they do not amount to any kind of speciesism. Just like the species arguments in Sections III and IV, they need not be restricted to any particular species like the human race, but may be applied to any biological group fulfilling the relevant requirements. More precisely, they may imply that any species capable of rational thought and/or moral behavior should avoid the dissolution of its biological boundaries, particularly when these are boundaries against nonrational and/or nonmoral beings. VI. ISAs AND GSAs In spite of their shared focus on biological realms and their corresponding boundaries, the two kinds of species arguments are clearly distinct in content. This is apparent in several respects: The species arguments in Section III are concerned with the moral status of individuals and confer protective rights on them due to their species membership. For instance, they state that if a sufficiently human HACH is not adequately treated, it may be degraded in its human dignity that originates from its species affiliation. As these arguments establish a standard of individual protection, I will call them “individual species arguments” (ISAs). The positions sketched in Section V, by contrast, address the moral integrity of groups and defend their ontological unity as a relevant demarcation against other communities. For example, they claim that the dignity of humankind may be threatened by the existence of sufficiently human HACHs, because they would blur the purportedly distinctive borders of the human species. Correspondingly, I call these types of arguments “group species arguments” (GSAs). ISAs are well known from debates on embryo protection or stem cell research (as well as the protection of severely mentally disabled people, demented persons, etc.), conferring protective rights on all beings belonging to humankind. GSAs, by contrast, are specific to the discussion of HACHs (or possibly genetically modified human beings, cyborgs, etc.), because the existence of semihuman entities could threaten the moral identity of humankind. Their common reference to species membership makes the two types of arguments appear similar at first sight. Interestingly, however, their presumptive consequences are almost exactly opposite with respect to HACHs: ISAs tend to claim protective rights for HACHs, denouncing their damage or instrumentalization or even calling for adequate support and developmental promotion. In line with this, they also refuse options like early termination, insertion of terminator genes (via ANT), or natural inability to develop (like in cybrids). At most, they would prefer a HACH not to be created at all if its proper treatment could not be assured. GSAs, by contrast, oppose the existence of HACHs even if their moral status were to be adequately respected. In line with this, they would definitely object to a HACH being generated and prima facie even demand its elimination once it had been produced. At most, they could accept a HACH’s creation in the case that it was complemented by options like early termination, terminator genes, or developmental inability if they concluded that species boundaries are not notably compromised, as long as no full-grown representatives of the corresponding mixture exist. I will shortly develop the logic of ISAs and GSAs in more detail. Particularly, I will sketch the ethical foundations on which GSAs may eventually be based (Sections VII and VIII). For the time being, however, I would like to emphasize the fact that we are confronted with two very different types of species arguments, referring to individuals or groups respectively, which are contrary in their normative implications but hardly ever clearly distinguished from each other (for an exception, see de Melo-Martin, 2008, 337–8). Furthermore, their constellation is quite unique to the question of human–animal mixtures, not extending to discussions, for example, on embryo research or stem cell harvesting, because GSAs have no application there. I propose that the relationship between ISAs and GSAs warrants closer investigation. Surely, not everybody will explicitly advocate ISAs or GSAs, let alone both of them at the same time. Still, their constellation may account for the peculiar moral confusion that HACHs excite and that I outlined in Section II. As I stated there, it is fairly possible that the idea of HACHs provokes contradicting intuitions within the same person at the same time—a drive to protect those beings and an impulse to eradicate them. We could shed some light on this apparently incoherent attitude if we were able to show that it rests on a specific interplay of ISAs and GSAs. Now, it is easy to identify the two intuitions with the opposing points of view that ISAs and GSAs respectively take—enforcing protective rights of HACHs (ISAs) and objecting to HACHs’ existence for transgressing species boundaries (GSAs). However, there is more to these arguments than just their contrary recommendations. In spite of their divergent content, they are interrelated in a more subtle way. Highlighting this relationship may help to understand better why those opposing viewpoints toward HACHs may coexist in the same mind simultaneously and thus induce a specific kind of normative disorientation. Apparent moral confusion could originate from a substantial ethical paradox. VII. TRANSCENDENTAL AND DIALECTICAL STRUCTURES OF SPECIES ARGUMENTS ISAs and GSAs are clearly distinct in their focus and implications. Yet, a closer look reveals that they stand in a rather intimate, essentially complementary relationship: ISAs admit certain beings to a protective community due to their species membership, without their having to prove their individual capabilities. This is due to the fact that ISAs are aligned to the idea of a moral union—advocating a concept of solidarity between the members of a lineage that excels by certain rational and/or moral properties, while being defined by its biological interconnectedness. For that argument to work, however, species boundaries need to be tolerably distinguishable and stable. The protective community into which those individual beings are to be received must constitute a recognizable natural realm with established boundaries—exactly what GSAs try to protect from critical dissolution. At first sight, this seems to imply that the relationship between ISAs and GSAs is one-sided, the first relying on the latter. But in fact, their connection is essentially reciprocal: In one respect, GSAs safeguard the basis for ISAs. They defend exactly those species boundaries on which the latter depend. In another respect, ISAs lay the foundations for GSAs. For in presupposing a sufficiently stable demarcation in order to mark their morally relevant communities, the former eventually provide an explanation as to why species boundaries should matter in the first place. Without giving further justification, it is hard to understand why species integrity should be a moral value at all (i.e., why the talk of “moral taboos” or “natural orders” has any relevant foundation). However, if it is a precondition for including individual beings into a protective union, the reason why species boundaries should have a normative import becomes more tangible (because these “taboos” and “orders” are essential for the assignment of individual rights). With some caution, we may call this bidirectional interdependence transcendental: The requirements of GSAs constitute a precondition for the application of ISAs. It is exactly this conceptual indispensability for ISAs, given their ethical import, that delivers the relevant justification for GSAs, as a necessary prerequisite for the moral ascription of fundamental rights.7 This normative relationship between two arguments, one relying on the other’s demands and thus providing the other’s justification, is quite intriguing. However, and even more interestingly, this connection becomes highly critical in the case of HACHs, as here the two types of species arguments collide: ISAs require their protection, even at early stages. At most, they may decide against their creation if it is not possible to warrant that protection. GSAs, by contrast, disapprove of their very existence and thus, prima facie, call for their destruction. At most, they may accept their creation if they were eliminated at early stages. As I noted in the introduction, I will not endeavor to carve out more precisely what kinds of HACHs (type and degree of chimerism or hybridization), at what stages of their development (embryonic, new-born, adult), or in what quantities (a few isolated laboratory individuals, a stable group engaged in self-contained procreation, a distinguishable lineage spreading into the planet’s wider biosphere) might be regarded as a substantial threat to species boundaries between human beings and animals. All I want to explain is why human–animal mixtures (at some point) may lead to a strange conflict of relevant arguments. HACHs may have moral status, due to their species membership, and at the same time undermine species integrity, due to their mixed set-up. In doing so, HACHs could establish an ethical impasse: They bring two types of arguments into moral opposition that are, in fact, ethically complementary. Such a constellation may provide a subtle reason for not creating HACHs in the first place, in order to prevent this kind of dilemma from arising. This is interesting insofar as, following this idea, it is not so much the separate arguments that reveal the fundamental problem of creating a HACH: independently, an ISA would just require that the HACH be adequately treated, merely denouncing its creation if that treatment could not be guaranteed, while a GSA would object to that creation as a matter of principle, even espousing termination once a HACH came into existence. Rather, it is the interplay of the two types of arguments that highlights the delicate problem with the generation of a HACH: once a HACH exists, the recommendations of ISAs and GSAs are paradoxically intertwined, because they still rely on each other while actually contradicting each other. In a way, their relationship becomes dialectical: They still depend on one another, by way of reference and justification. Yet, they also negate one another because ISAs require the new being to be protected while GSAs require terminating its existence.8 One may be inclined to think that a GSA need not pass from its primary claim that a HACH should not exist to the further demand that a HACH be terminated: it might be exactly the force of an ISA that kept us from progressing from the first idea to the second. Consequently, the objection might go, there is no real paradox at work. Rather, what we find is the common phenomenon of some mutual balancing between opposing views. However, the simple fact that an ISA is needed in order to prevent this transition indicates that there is a deeper problem involved here: without such interference, the GSA’s suggestion that a HACH should not exist would imply the requirement that a HACH be terminated, as any complaint against a thing’s existence prima facie calls for that thing’s removal. Possibly, the ISA’s resistance might be strong enough in order to block that transition of the GSA, but still the essential demands of the two arguments conflict with each other. At the same time, however, both arguments derive their respective cogency and strength from the fulfillment and force of the other’s requirements. Even the ISA cannot favor a HACH’s continued existence without ultimately threatening its own basis, just as the GSA cannot call for a HACH’s destruction without eventually questioning its own foundation. This makes the interplay of ISAs and GSAs more tenuous than just a simple weighting of different standpoints. These ethical considerations may explain at least some of the moral ambiguity that HACHs entail. In particular, the ethical puzzle that HACHs establish by bringing two species arguments into conflict that are actually interdependent may explicate why the idea of HACHs can conjure up contradictory moral impulses to protect and to terminate within one and the same mind. These impulses need not be akin to the rash and similarly inconsistent feelings that, for instance, images of severe misery and suffering sometimes evoke—nourishing drives to help and to run away, to support and to get rid of, all at the same time. Rather, they may resemble the well-grounded and justified disorientation that one can experience after having made a first moral mistake, like a promise to a defrauder to not betray him—leaving one with divergent obligations, to keep and to break one’s word, simultaneously. The ethical dilemma that such a promise induces is not the least important argument against making it in the first place. Similarly, avoiding the ethical dilemma that a HACH could generate for the interplay of ISAs and GSAs may constitute a serious argument against the HACH’s very creation. The difference is that, in the case of the promise, the divergent obligations need not be intimately related to each other but may stem from largely independent moral sources, such as personal duties to fidelity and impartial obligations of justice. In the case of the HACH, however, the opposing demands are indelibly intertwined, which makes the dilemma particularly pressing (two demands contradict and still support each other) and at the same time highly stable (you cannot simply drop one demand to satisfy the other because it is presupposed by the other). A HACH may have protective rights, according to ISAs. At the same time, a HACH may dilute recognizable species boundaries, which are demanded by GSAs. Thus, an ISA will opt for a HACH’s protection, whereas a GSA will opt for a HACH’s elimination. In spite of this plain opposition, neither argument can simply reject the other, because ISAs establish their ethical protection by appealing to fixed species boundaries as demanded by GSAs, while GSAs obtain their ethical justification as necessary preconditions for the functioning of ISAs. In this way, a HACH is at the same time worthy of individual protection and a threat to an essential order, as the ambiguous feelings toward it suggest. This ambiguity, however, is truly deep and not easily resolvable, because a HACH threatens exactly those standards on which its own protection may ultimately be based. This does not only imply that HACHs, in a way, undermine their own existence: they dissolve species boundaries that are essential demarcations along which the protection of certain beings, HACHs included, may eventually be articulated. It also means that the relevant arguments, ISAs and GSAs, are contained in a stable impasse: they presuppose each other so that giving up one in order to satisfy the other is not an option (hence the possibility of encountering their corresponding moral stances within one person) while at the same time they are entangled in a straightforward contradiction (hence the existence of moral confusion in that person). VIII. RELATED POSITIONS The idea that the preservation of certain biological boundaries may be a necessary condition for the functioning of fundamental moral norms is not uncommon in bioethics. For instance, some authors suppose that the unchanged genetic constitution of human beings or the biomedical intangibility of early human embryos is a necessary condition for holding up elementary protective standards that are crucial to our general moral practices. In line with these arguments, changes in human genetics or experiments on human embryos may not, by themselves, violate individual rights. Nevertheless, they may undermine the moral framework on which such rights ultimately depend. Annas and colleagues regard “[m]embership in the human species” as “central to the meaning and enforcement of human rights.” They proceed to argue that human cloning and genetic interventions might “alter the essence of humanity itself,” thus threatening “to change the foundations of human rights” (Annas, Andrews, and Isasi, 2002, 153). While I do not necessarily approve of the authors’ specific metaphysical appraisal of how genetic changes might affect human nature, I do agree with their basic normative presumption concerning the reference of ISAs to GSAs: human beings are to be respected due to their individual species membership (ISA), while fixed species boundaries are essential for the assignment of such individual species-related rights (GSA). Habermas states that eugenic manipulations of human embryos cannot be criticized within “the moral language game itself,” by way of “moral argument,” for example, by claiming that human embryos have individual rights and that those rights are violated by such practices. However, eugenic manipulations threaten “the preconditions for preserving a moral self-understanding of persons,” thus being open to normative criticism from “a species-ethical understanding that cannot be squared with the heedless optimization and self-instrumentalization of prepersonal life” (Habermas, 2003, 92, 94). Although I am more positive concerning the moral attribution of individual rights to human embryos, I endorse the general idea that certain practices can affect the normative foundations of protective standards as such: intervening in human species identity may undermine the very basis (the “species-ethics”) for attributing individual rights to human beings (within the “moral language game”). Both arguments point to the transcendental character of certain norms, similar to the structure that I sketched in Section VII: They contend that some biomedical action is not problematic for being an immediate infringement of somebody’s rights (it does not directly conflict with an ISA). Rather, it destabilizes a moral framework on which such rights are ultimately based (they conflict with a GSA on which the functioning of ISAs eventually depends). The case of HACHs is special, however, because it turns this transcendental relation into a dialectical structure, as outlined in Section VII: HACHs themselves may be candidates for being assigned individual rights of protection (due to an ISA). At the same time, HACHs may violate the very basis of such protection and thus undermine the cogency of their own rights (due to a GSA on which ISAs rely). IX. TWO OBJECTIONS It may be objected that this conclusion is imprecise for two reasons: First, a HACH’s protective rights need not be based on species arguments but may be derived, preferably, from capacity or potentiality arguments. Because these do not refer to species membership, they are unaffected by the HACH’s crossing species boundaries so that the alleged dilemma does not occur (if you do not use an ISA to protect a HACH, you need not care if the HACH undermines a GSA). Second, ISAs refer to the species of the HACH, to the kind of community that its own biological line establishes. The HACH itself, in turn, disrupts the boundaries of other species, namely, the species that are united within it, so that no direct contradiction with a corresponding GSA obtains (if you protect a HACH with regard to its own species, you need not care if the HACH blurs the distinctions of some other species). As to the first point, I completely agree that the critical constellation I have accentuated is restricted to the application of species arguments. It does not pertain if the moral status of HACHs is established with respect to their capacity or potential (rather than along an ISA) and if species boundaries are regarded as normatively irrelevant (contrary to a GSA). But the aim of my argument is not so much a normative one, prescribing which arguments should be brought forward in discussions of HACHs. Rather, my main point is analytical in nature, trying to highlight the interplay of different arguments that are shaping the discussion. More precisely, I want to show that some of the moral confusion concerning HACHs may be traced back to an ethical dilemma of arguments that are sometimes (and not arbitrarily) applied to them. If someone should take this result as a reason for aggravated reservations against species arguments, rather than against HACHs, I find this conclusion comprehensible (though not inevitable). Regarding the second point, I am not sure that things can be disentangled so easily. On the one hand, it may well be that one would want to declare a sufficiently human HACH to be a member of the human species, and to protect it accordingly, in line with an ISA. This would pose a problem if such a HACH undermined human species identity at the same time. On the other hand, an ISA might refer to the particular new species of the HACH and regard this species as a kind of community from which an individual member’s protective rights should eventually derive. Even this kind of argument, however, is weakened if the existence of the HACH, as a mixed being, generally dissolved the kind of boundaries that its protection was based on in the first place. In both cases, our moral intuition to protect this being because such beings share certain features is eroded, if the biological set-up of “this being” challenges our classificatory notion of “such beings,” either in that particular instance or in a general fashion. X. CONCLUSION In a recent publication, Haber and Benham argue that the central problem of HACHs is not the moral confusion that their existence might provoke but uncertainty concerning their moral status: This status depends on both their origin and their abilities, which would have to be properly assessed before we can know how to treat them. Uncertainty with respect to these factors, however, supports a precautionary principle that might lead us to abstain from their creation or even legally to prohibit their production (Haber and Benham, 2012, 23). The argument explored in this paper is different, in that it does not rely on uncertainty concerning moral status but rather on some ethical contradiction that this status is apt to imply: HACHs may turn out to have moral status, with respect to their capacities, their potential, or their species membership. At the same time, HACHs shake the normative foundations of the latter argument. Apparently, HACHs conjure up a conflict between two distinct types of species arguments: They may derive protective rights from ISAs because of their belonging to a corresponding biological community. At the same time, they are objectionable in the light of GSAs because they undermine the very idea of identifiable biological realms. However, because these conflicting arguments are mutually interdependent, HACHs eventually question the basis of their own existence: They derive protective rights from an ontological membership while their mere presence disturbs just this conception of a biological community. This profound ethical dilemma may be the deeper foundation of “inexorable moral confusion” that human–animal mixtures have been famously predicted to evoke within human thinking and acting (Robert and Baylis, 2003, 9–10). NOTES 1. This is the basic criticism of speciesism, as famously formulated by Peter Singer (see Singer, 1993, 55–68). 2. Unfortunately, accusing species arguments of speciesism has become a notorious mistake in bioethics in general and in HACH discussions in particular (see, e.g., Piotrowska, 2014, 5, 7–8). 3. One may doubt, notwithstanding the arguments sketched below, that rationality or morality should be regarded as relevant features for protective rights. Instead, one may prefer to base moral status exclusively on capacities like sentience and suffering, in line with the utilitarian tradition. Still, it is a formal mistake, for the reasons given above, to accuse species arguments of speciesism, that is, of drawing an arbitrary line between humans and nonhumans. There are clearly nonarbitrary reasons for that distinction. 4. This may concern special kinds of action, such as buying or owning such a being, which may still be legitimate. It may also concern the proper balancing of the being’s rights against other beings’ rights, for example, its killing in order to save a rational and/or moral creature, which may also be assessed as adequate. 5. What needs to be distinguished here is the basic explanation and justification of moral status (referring to the specific dignity of autonomous beings, as established by fundamental ethics of personhood) and the concrete attribution of this status to individual entities (referring to an inclusive community of human beings, to be exemplified by political philosophy of rights). The latter is no arbitrary and gratuitous extension of protective rights beyond a frame that was firmly and conclusively established by the former. Rather, specifying the assignment and range of rights is a necessary completion to the foundation of their essence and logic. In this sense, it is common and vital that political philosophy, with its own instruments and categories, clarifies who exactly can claim those rights, the basis and contents of which have been disclosed by fundamental ethics beforehand. 6. Note that, while it may seem reasonable to apply a species argument in order to protect a nonrational, nonmoral member of a rational, moral species against instrumentalization, it would appear nonsensical to produce a species argument in order to protect a nonsentient member of a sentient species against suffering. For whereas the nonrational, nonmoral being still can be instrumentalized, the nonsentient being simply cannot suffer. 7. This mutual interdependence rests, in fact, on a stronger basis than just on some practical advantage or epistemic convenience: it is not only that, for an ISA, it would be difficult to tell which beings belong to the same species if there were no fixed species boundaries, as demanded by a GSA. Rather, an ISA would lose its very conceptual foundation if species boundaries were effectively dissolved. So, the relationship between the two arguments is very tight indeed: without stable species boundaries, we do not just face a pragmatic problem of identification, not knowing which criteria to apply when assigning individual organisms to biological groups. Rather, we get a theoretical problem of classification, eventually losing the very meaning of the distinction we want to make use of. 8. This strange constellation is more precarious than seemingly similar cases where only some past procedure, but not the present product, may appear reprehensible. For instance, one may object to certain modes of creation, such as in-vitro fertilization (IVF), prenatal genetic diagnostics (PGD), human cloning or, obviously, rape (because one holds that they constitute acts of objectification, instrumentalization, maleficence, etc.), without resenting the creature obtained, that is, the embryo generated, the fetus selected, the human cloned or the child conceived (particularly as they are not ontologically different from embryos, fetuses, humans, or children obtained in inoffensive ways). Accordingly, on the one hand, one may hold that the procedure in question (IVF, PGD, cloning, rape) should not be performed and that in this sense the corresponding being should not come into existence, while still, on the other hand, granting the product (the IVF embryo, the PGD fetus, the clone, the rape child) full moral status once it exists, without any contradiction—because there simply is no reason to eliminate it. With HACHs, however, the case is different, or even reversed. Here, the creature itself appears problematic, as stated by GSAs (because of its ontological peculiarity of having a mixed-species setup), while the act of creation as such may actually prove to be harmless (because it need not infringe any norms of nonobjectification, noninstrumentalization, nonmaleficence, etc.). Accordingly, the very existence of a HACH poses a problem (supposedly disturbing some relevant natural or social order) and for that reason the corresponding being should be prevented from coming into existence, and also, prima facie, be terminated once it exists, in line with a GSA (in order to restore that order)—in clear contradiction to its supposed protective rights, as supposed by an ISA. ACKNOWLEDGMENTS This work has been developed as part of the author’s philosophical research in Unit 10.7 “Ethical and Legal Dimensions (ELD)” within the Cluster of Excellence REBIRTH—From Regenerative Biology to Reconstructive Therapy, hosted at Hannover Medical School (MHH), Germany. The author would like to thank Lucie White for extremely valuable discussions, Lucie White and Koko Kwisda for shared research into the general structure of ethical arguments on human–animal chimeras and hybrids, as well as two anonymous reviewers from The Journal of Medicine and Philosophy for helpful comments on earlier versions of this paper. REFERENCES Academy of Medical Sciences. 2011. Animals containing human material [On-line]. Available: https://acmedsci.ac.uk/file-download/35228-Animalsc.pdf (accessed January 10, 2018). Annas, G. J., L. B. Andrews, and R. M. Isasi. 2002. Protecting the endangered human: Towards an international treaty prohibiting cloning and inheritable alterations. 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Published: Apr 1, 2018
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