Species membership and potentiality
From all of this it may seem that only a human species membership or potentiality- based criterion of personhood status can avoid the various reductios. A potentiality theory of moral status can come in more than one form. Most basically, however, potentiality reasoning posits that the correct criterion of moral status is a creature’s future potential to become a fully realized person. On this reasoning, it may still be true that personhood requires meeting some threshold of psychological capacities. However, the important quality for full moral status and the right to life is only that of potential personhood. The attractiveness of the potentiality criterion lies in the fact that it confers full moral status on both infants and human beings in reversible comas on the basis that, although they do not currently exercise the traits characteristic of personhood, they have the capacity to exercise them in the future.
Michael Tooley has argued that anyone defending the proposition that human beings are persons from conception are in fact forced into a dilemma whereby they must choose between a potentiality basis for moral status or a morally arbitrary, ‘speciesist’ preference for human species members. If one wishes to avoid a pure species membership criterion, only the potentiality principle can tell us why human infants, let alone fetuses, have full moral standing, since infants seem not to meet the conditions for personhood on any non-speciesist account. Thus Tooley thinks that both the pro-life case and the equal moral status of infants stand or fall on the success of such a principle. Although human fetuses and infants do not possess the psychological capacities sufficient to qualify for personhood (on Tooley’s reasoning), they do possess the potential for those capabilities. Only if this potentiality is status-conferring, then, will they be owed a strong right to life.
Plenty has been written about the potentiality principle, which has been widely criticized by many accounts of moral status. I will make only a few points here, mostly relevant to the reductio problems that potentiality, or, indeed, anti-potentiality, reasoning throws up. To clarify, the potentiality principle ties moral status to facts about a creature’s capacity or future potential to realize certain goods or capacities typically associated with personhood, like the capacity for rational thought or the conscious desire for continued life. A potentiality criterion of moral status is therefore able to avoid episodic problems concerning human beings in comas and those with no current desire to live. Such beings still have the capacity for rational thought or conscious desires, and that is what counts. Such theories also have no problem accounting for the moral status of infants, who also possess the relevant potential, even if they do not have the current capabilities of persons.
The price for this, or the pay-off, depending on one’s outlook, is that the potentiality criterion seems to confer equal moral status on human embryos or fetuses, which also possess the capacity for future rational thought processes, conscious desires, or whichever other cognitive-based capacities one takes to constitute personhood. The problem here is how to distinguish between the kind of potentiality exhibited by infants, sleeping people, or the comatose, and that exhibited by embryos and fetuses. Of course, a sleeping or comatose adult may not be currently exercising her capacities for conscious thought, but she has certainly exercised that capability in the past. Moreover, it might be argued that sleeping or comatose adult human beings possess the mental apparatus for the relevant kinds of cognition, even if it is not currently operational, whereas fetuses, certainly up to a late stage, do not. The former beings, we might say, have cognitive capacities that are immediately exercisable, unlike nascent human beings, whose potential is still future and theoretical.
We can think of cases, however, of which this is not true. Take, for instance, someone who is comatose due to temporary brain trauma, and who has the capacity to regain normal cognitive functioning, but only after a period of brain regeneration. Such a person does not have a current or an immediately exercisable capacity for, say, rational thought, self-awareness, or conscious desires. Added to this, it is not clear how a personhood criterion based on ‘immediately exercisable’ cognitive capacities would accommodate the moral status of neonates or slightly older infants, whose potential for higher thought processes is not immediately exercisable. Whether the immediate/non-immediate distinction draws acceptable boundaries regarding who is in and who outwith the category of persons, we still need some kind of justification for treating the kinds of potentialities differently. Some are understandably sceptical about any such justification. As the philosopher Patrick Lee writes:
What matters is that the difference between the kind of potentiality a human embryo or fetus has (not immediately exercisable) and the kind that a sleeping person has (immediately exercisable) cannot carry the moral weight which proponents of this position load upon it.
For those that endorse it, the potentiality principle is the antidote to cognitive- based criteria of moral status, which exclude too many obviously rights-bearing human beings from the personhood category. It is widely taken to correspond with the conception threshold of moral status, since this is when an individual being with whom we can identify the relevant potential arrives on the scene.
But potentiality criteria of moral status also appear to be subject to reductios in being both over- and under-inclusive. One reductio, depending on your point of view, is precisely that the potentiality principle puts embryos and fetuses on a par with all born human beings, infants, and adults, in terms of moral status. Thought-experiments like the Embryo Rescue Case show this to be deeply counterintuitive. As will be remembered, the Embryo Rescue Case asks you to imagine that you are about to flee a burning hospital and have the option of grabbing and rescuing either five human embryos or one fully formed human baby. Most people consider it unthinkable—probably even morally impermissible—to choose to save the embryos rather than the baby, even though they number five and the baby only one. If this intuition is correct, it can only be because the moral status of the baby vastly outweighs that of an embryo, such that, even though the embryos are greater in number (and all things being equal, one ought to save the many over the few), saving the baby is the only reasonable course of conduct.15
Any persuasive potentiality principle must also advance an intelligible rationale for making potential personhood the condition of moral status. Those charged with the task of formulating such a rationale immediately face a simple problem. This is that it is difficult to see why being a potential person should endow a being with the same moral status as an actual person. Being a potential person means that a being is, by definition, not an actual person. Why, then, should such a creature enjoy the rights and status that attends actually realized personhood?
One possible answer to this might be found in the philosopher Don Marquis’s ‘future like ours’ argument in defence of the potentiality principle.  Marquis begins his argument against abortion not by asking what features are constitutive of personhood, the typical approach, but by asking instead why it is usually so wrong to kill adult human beings. He answers this by claiming that the essential wrongness of killing adult human persons lies in the deprivation of their future, a future which would be characterized by all of the quintessential goods of human life, such as rational and other higher thought processes. Thus it is that killing a person painlessly in her sleep is no less of a wrong qua killing than a brutal murder. The deprivation of a future of value—the core wrong-making factor in killing—is inflicted on the victim regardless of any other features of a killing, such as the pain experienced by the victim.
Marquis’s next move is to point out that embryos and fetuses also possess a future which will include the goods of distinctly human flourishing—‘a future like ours’. Thus, if the essential wrong-making factor in killing us, persons, is the deprivation of our future, then killing embryos is just as wrong for exactly the same reason: that it deprives them of the same kind of future.
Marquis’s theory seems to entail the equal moral status of embryos, fetuses, and all born human beings, at least when it comes to questions about the permissibility of killing. However, it also seems to bear out the deeply counter-intuitive implication that killing an embryo or a zygote which has just come into existence is the worst kind of killing there is, because it involves inflicting the greatest loss of future (human embryos that will not die in utero probably have a lengthier valuable future ahead of them than I have). This seems to prove too much, and to place far too much significance on fertilization as an event of hugely moral import. Could it really be correct that the difference fertilization makes is the difference between no meaningful loss of life, where two gametes about to fuse are destroyed, and the most serious loss of life that there is?
Potentiality principles of moral status (whether Marquis’s version or others) might equally prove too much in some other respects. If the relevant potential is taken to be only theoretical potential—meaning, the future potential to embody distinctly human forms of flourishing in the right circumstances, then it appears to confer full moral standing on too many kinds of beings. Jeff McMahan provides an imaginary example in which we discover that dogs have the potential to develop cognitive capacities similar to that of a normal five-year-old, but that this potential can be realized only by subjecting the dog to an intensive regimen of cognitive therapy for the first five years of its life. If we do not think that all dogs, by virtue of this discovery, possess moral status equal to all born human beings, then ‘mere potential alone is not sufficient to bring a being within the scope of the constraint’.!® As McMahan claims, the intuitively sound reaction to this sort of scenario seems to be to say that although all dogs have an interest that their potential is realized, this alone does not grant them any more moral status unless and until it is.
Alternatively, if the criterion of moral status is not theoretical but actual potential—in other words, the fact that, if not interfered with, a creature will come to acquire higher cognitive functioning or a ‘future like ours’—that criterion seems to be overly exclusive. There are some born human beings which do not function rationally, or embody other distinctive forms of human flourishing either actually or potentially, such as human beings with radical cognitive deficiencies. Although it seems incorrect to exclude such human beings from the category of persons, it does not look as though mere potential personhood, where that potential is of the kind that can and will be realized, is a basis for ascribing them moral status.
The same, of course, can be true of both infants and fetuses, depending only upon their individual prospects. McMahan points out, for example, that viable fetuses which are severely, congenitally, cognitively impaired lack an actually, realizable potential of the relevant kindd9 The same can be true of severely disabled infants. On the actual potentiality criterion, we apparently get the result that a woman can permissibly have her fetus or infant destroyed if it has no prospect of meeting a certain threshold of cognitive functioning, but not otherwise. Moreover, it will not be an answer to this to state that being a potential person or being a born human being with no similar potential both suffice individually to qualify for strong moral rights. The entire pay-off of potentiality reasoning is that it is meant to overcome the speciesism objection to a pure species membership criterion of personhood. Suggesting it as merely a second, alternative, sufficient criterion for personhood therefore does nothing to solve the problem in response to which it is introduced.
Certain defenders of the view that personhood begins at conception would likely respond by claiming that I am defining the potentiality principle incorrectly.
Instead of pertaining to either theoretical or actual potential for certain cognitive capacities, or a certain kind of future, some have suggested that the morally relevant kind of potentiality is the ‘radical’ capacity for these traits which all human species members possess by virtue of their genetic code, whether they are ever able to realise that capacity or not.2° According to Kaczor, for instance, all creatures belonging to the natural kind ‘human being’ have those capacities encoded in their genes, and are thus properly described as ‘rational beings’, whether or not they are ever able to function rationally. He writes:
Rational endowment is nothing other than the capacity, ability or disposition (though perhaps not realizable) enjoyed by whole, living beings whose active self-development is aimed towards and whose flourishing consists in freedom and rationality^1
In saying that a zygote’s ‘flourishing consists in freedom and rationality’, Kaczor means to say that forms of flourishing and cognitive functioning which typify normal, developed members of the human species (and distinguish us from non-human animals) are the benchmark against which the good of all species members are evaluated, and he elaborates this point elsewhere. For example, the inability to read, or to communicate using language, constitutes an unfortunate lack of flourishing for a ten-year-old child, but not so for a cat. A cat’s failure to reach those benchmarks is not deemed lamentable like the child’s, precisely because reading and speaking do not constitute typical forms of flourishing qua cat. Consequently, Kaczor writes, even though not every human being can communicate, is consciously aware, and so on, ‘every single human being is nevertheless properly described as a rational being. Not a potentially rational being, but a currently existing actual rational being.’22
To underscore the point, Kaczor provides an analogy. ‘To say that the human being in utero is not a rational being because he or she is not functioning rationally’, he writes, ‘makes as much sense as saying that a human being is not male or female unless in the act of successfully reproducing’^  He suggests that just as a human being can be biologically male or female regardless of their ability to perform activities specific to their sex (i.e. perform a male or female reproductive role), so a human being who never possesses reasoning ability is still rational. The analogy seems somewhat inapt, if only because reproductive potential does not appear to be integral to any definition of ‘male’ or ‘female’. The core suggestion, though, is that rationality is a defining capability of human beings, and that all human beings are therefore latently rational, whether or not they are ever actually capable of reasoning.
Arguments such as these have been collectively referred to as ‘nature-of-the-kind’ arguments about moral status, and I will return to look at them more closely in due course.24 For now, the question is whether arguments like this can salvage the potentiality criterion for full moral status. As I see it, they cannot, because they instead replace that criterion with something else. A ‘radical’ potentiality criterion which looks only to whether a creature has the genetic coding of a species that typically exhibits person-like traits might well dodge some problems of over- and under-inclusiveness. For instance, it would not include all of the dogs yet to be equipped with higher cognitive faculties in McMahan’s science fiction scenario. And it would include infants and the radically cognitively impaired, since such human beings still have the ‘radical’ capacity for uniquely human cognitive abilities even if they do not, and never can, realize it. However, the new criterion is only able to do this by dropping potentiality as the morally significant feature completely, and endorsing instead a simple species membership criterion of personhood.
Either potentiality (theoretical or actual) matters for moral status, or it does not. If it does, then the various counter-examples which seem to show potentiality reasoning to be over- or under-inclusive are live objections. If it does not, then we are no longer confronted with a recognizable instance of a potentiality-based theory. But once potentiality is dropped out in favour of a pure species membership criterion of moral status, the other horn of Tooley’s dilemma closes in. That criterion will amount to mere speciesism unless a convincing theory that ties moral status to human species membership can be offered.
In summary, the potentiality criterion for moral status is highly problematic for much the same reason that psychological criteria seem to be: that it cannot be grounded in a rationale which draws the boundary lines for morally considerable beings in a way that we would deem acceptable. On the other hand, once the independent value of future potential is altogether removed from our determinations of moral status, we do indeed seem stuck with how to explain the moral status of infants or the comatose in a way which does not fall back on a form of speciesism, let alone that of human beings with radical cognitive deficiencies, whom it may seem can be accounted for only by a pure species membership criterion.
At this point, one may want to change tack entirely and propose a bare sentience criterion which accords full moral status to all creatures capable of conscious, sensory experience, regardless of their further cognitive capacities. It might be thought that a bare sentience criterion tracks a middle way between a pure species membership basis for personhood, which seems insufficiently justified, or a psychological criterion, like rationality or agency, which is unpalatably exclusionary. However, 
it will be difficult to explain why a bare sentience condition would not accord the same level of moral status to all sentient creatures, human and non-human. Most non-human animals, even those that lack sophisticated mental states, are at minimum sentient beings. That is, they are capable of subjective experience: they touch, taste, smell, and feel, and there is something it is like to be them. This is as true of birds and mice as it is of humans. A bare sentience condition of personhood would therefore appear to be overly inclusive in its extension of full moral status to such creatures, unless, that is, it is a threshold for moral status limited to human beings. How, though, would one explain this additional species membership condition without once again inviting the speciesism charge?
-  Tooley (n 7).
-  Patrick Lee, Abortion and Unborn Human Life (2nd edn, Catholic University of America Press2010) 26.
-  Defenders of the conception threshold have advanced a number of debunking explanations forthe common intuition in the Embryo Rescue Case, the conclusion being that the intuition is notincompatible with the view that personhood begins at conception (see Kaczor (n 9) 146 and RobertP George and Christopher Tollefsen, Embryo: A Defense of Human Life (Doubleday 2008) 138—42.Since there is not enough space to review those arguments here, I will simply say that I find them to beunconvincing primarily because they fail to dislodge the very compelling notion that the explanationfor the common conclusion that one ought to save the baby rather than the embryos is that the baby isintrinsically more morally valuable a being than the embryos, and not some other explanation.
-  Don Marquis, ‘Why Abortion is Immoral’ (1989) 86 Journal of Philosophy 183.
-  Jeff McMahan, ‘Infanticide’ (2007) 19 Utilitas 131, 145. 1® ibid 145. 19 ibid 144.
-  ° See, for example, Patrick Lee, ‘The Basis of Being a Subject of Rights’ in John Keown and RobertP George (eds), Reason, Morality and Law: The Philosophy of John Finnis (Oxford University Press2013) 242. Lee defines creatures which possess the ‘radical capacity for rationality’ as those ‘having aconstitution or nature orienting one to active development to the stage where one does perform suchactions—as opposed to an immediately exercisable capacity’.
-  21 Kaczor (n 9) 106. 22 ibid 107. 23 ibid.
-  Kaczor’s reproduction analogy raises plenty of questions all by itself, such as whether we, orindeed all things, are defined by our latent or theoretical, although in actuality inexpressible, characteristics. It is not unthinkable that I could have been a gymnast, although I cannot possibly be one now,and probably never would have been one. Is ‘gymnast’ one of my defining characteristics? Kaczor maysay that it is only those characteristics which human genetic coding makes possible that are definitiveof all of us, but this does include the characteristic of being a gymnast, being a zookeeper, a linguist,or anything else only human beings can be or be like (psychopathic, for instance). Kaczor will needto explain why, on his understanding of defining characteristics, all of the capacities which uniquelyhuman genetics make possible are not defining traits of every species member, or if only some, whichones, and why.