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Is the Human Person a Substance or a Property-thing?

J.P. Moreland and John Mitchell, Ethics & Medicine 11.3 (1995), pp. 50-55.

In an era where the defence of human rights is prominent, a fundamental question is who counts as a human person and, more specifically, when does human personhood begin and end? The answer to the question at both ends of the spectrum requires metaphysical reflection in three areas: 1. What is a substance and what is a property-thing?; 2. What does it mean to be a human being?; and 3. What does it mean to be a human person? In this paper, we will address these questions in order to lay a metaphysical foundation for ethical decision-making concerning human rights at the edges of life. While the implications of this analysis extend to a variety of ethical issues, we will limit our application to the ontological status of the unborn, and argue that zygotes, embryos and fetuses (hereafter referred to synonymously) are fully and equally human beings, and consequently, human persons. We shall not address the abortion question directly, though we trust the implications of the arguments presented will become obvious.

Substances vs. Property-Things

Central to the task of developing an ontology of unborn human beings is the distinction between a substance and a property-thing. According to the traditional view of Aristotle and Aquinas, acorns, dogs and human beings are examples of substances. Every substance is an individuated essence that bears accidental properties and exists as a deeply unified whole that is ontologically prior to its parts; that is, a substance is more than the aggregate or emergent sum of its parts and properties. Most importantly, a substance possesses a defining, internal principle or essence that informs its law-like change and behaviour. By contrast, an artifact is a property-thing or ordered aggregate. A Ford Aerostar is an example of such an entity, existing as a loosely unified aggregate of externally related parts. There is no underlying bearer of properties existing ontologically prior to the whole, and no internal, defining essence that diffuses, informs and unites its parts and properties. It is merely a collection of parts, standing in external, spacial-temporal relations which, in turn, gives rise to a bundle of properties determined by those parts.

The same is not true with a substance, say a dog. The properties of a dog inhere differently from the properties of an automobile. The adherent properties of the dog are grounded in and unified by the capacities that constitute the internal structure of the dog’s essence. Thus, a dog is more than the external organization of its parts functioning in a given way. Its properties are deeply unified and related internally as part of the essential nature of ‘dogness’. A dog is what it is without convention and its properties exist only in the context of a coherent, ontological whole. By contrast a Ford has no ontology beyond its additive or emergent properties, bundled together to form the whole. Lacking an internal essence or nature, an ordering principle is externally imposed upon a set of parts to form a bundle of properties by human convention. To possess an internal nature, then, is possible only for substances, all of which belong to a natural kind or Infirma Species. They exist in a manner essentially unique to a particular class of beings. Their essential nature informs their being and affords the essential properties peculiar to their natural kind. All members of a given species instantiate the same essential nature. It is, therefore, unintelligible to assert that a substance can exemplify its nature to a greater or lesser degree, since the essential nature underlying a given member of a species is non-degreed. That nature either is or is not exemplified by some particular.

While substances possess an internal nature, property-things do not. There is no internal, ordering principle to ground its unity, nor to ground law-like change or guide the movement of an automobile toward an ontological telos. There are only modifications caused by external forces. Specifically, human minds designed and built the automobile by configuring its materials into a functional pattern. These materials had no proclivity to be so structured, and are externally related in an artificial pattern. The shape, location and function of the materials could have been radically different and each component could have been used for an entirely different purpose from constructing an automobile. By contrast, that which moves a puppy to maturity or an acorn to a mature oak tree is an internal, defining essence or nature. This nature directs the developmental process of the individual substance and establishes limits on the variations each substance may undergo and still exist. The acorn will not grow into a dog and the dog will not become an oak tree. Consequently, a substance functions in light of what it is, and maintains its essence regardless of the degree to which its capacities are realized. Thus, while morphology and the degree of functional expression may vary among members (individual substances) of a natural kind, such variance does not affect the essential nature of their being. For it is the underlying essence of a thing, not its contingent state of development at a given point that constitutes what it is. We would not, for example, say that an oak sapling is of a different kind from an adult oak tree. In general, as a substance grows, it does not become more of its kind, but rather, it matures according to its kind.

As Aristotle argued, as a substance changes, its potentialities or capacities become actualized in a way that is, at once, controlled by and a reflection of the structure of that substance’s essence. The capacities for the acorn one day to develop a trunk, branches and leaves are already embedded within the acorn, prior to their realization. This is true whether the acorn actually grows into a tree or not, since such development is dependent on accidental conditions that are wholly independent of the acorn’s essential nature. When such conditions are met, however, including the proper soil, environment, etc., the acorn will express its latent capacities in the proper way. The absence of such conditions is irrelevant to the essential nature of the acorn.

The nature of potentiality and actuality, as it is found in substances, exhibits a hierarchical structure of capacities. To clarify what is meant here, consider Smith, a human being. Smith has the first order capacity to speak and write in English. He also has the second order capacity to develop the first order capacity, currently lacking, to speak and write in French. Smith’s capacities proceed in a hierarchy until ultimate capacities are reached. These constitute Smith’s human nature and they exist in Smith as long as he has being. In general, a substance’s inner nature can be understood as a unity of a substance’s ultimate capacities possessed by it solely in virtue of its membership in its natural kind.

A further distinction between substances and property-things follows from the above discussion. Specifically, substances maintain their ontological identity through change, while property-things do not. An individual substance endures through change because it is more than the aggregate set of its parts or a bundle of properties, formed according to an external ordering principle. The accidental properties or parts of a substance can change without altering the thing itself. This is true because it exists as a deeply unified, ontological whole that possesses its properties and parts. A dog for example, can lose a tooth or shed its fur, but remain the same dog throughout these processes of change; for the dog is not an aggregate sum of its parts or an emergent whole whose parts are prior to the whole. Instead, the whole is prior to the parts and they exist in virtue of their internal relations to each other, grounded in the enduring essence of the dog. By contrast, a property-thing cannot sustain identity through loss or gain of parts. Mereological essentialism would seem to characterize a property-thing. No single entity endures through change; rather, a property-thing is an entia successiva, a space-time worm. Since property-things are identical to the sum of their bundled properties and/or ordered parts, a change in any property or part necessarily causes one ‘entity-stage’ to end and another to begin. Property-things have no enduring essences to ground their sameness through change.

The Human Being as a Substance

Regarding the theme of this paper, it is arguably the case that a human being is not a property-thing but a substance. Space does not permit a detailed defence of this claim beyond what has already been said to this point, but it may be helpful to sketch four main lines of argument relevant to such a defence. This will at least set out in explicit form just what the major metaphysical issues are in defending or attacking the view that a human being is a substance. First, a case can be made that the different structures of consciousness, as well as
the different bodily organs stand to each other in internal relations and exist as parts or structures whose identity presupposes the whole of which they are parts or structures. Second, absolute personal identity through change is still defencible in light of first-person irreducibility, introspective awareness, and the various inadequacies of ancestral chain models of personal identity. Third, humans exhibit species specific capacities for law-like stages of development that run throughout all the members of the kind ‘human being,’ and there are types of changes such that, if they obtain, we would no longer claim that a human being is present. Finally, libertarian free will is a defencible view of freedom and it has as a necessary condition an agency model of human action (either agent causation or a non-causal theory of agency) which, in turn, has as a necessary condition, a substance view of the actor.

Now, each of these four metaphysical claims has been disputed, and while we cannot defend them here, it is still crucial to point out that if these theses are true for human beings (they are organic, non-emergent wholes who exhibit absolute personal identity through change, law-like stages and limits to development, and libertarian freedom), then human beings are substances and not property-things. Before we move on to an application of the preceding discussion to the question of the ontological status of the unborn, we want to look briefly at three objections to the view that humans are substances. These criticisms zero in on problems with the notion of an essential nature.

First, some claim that the classical doctrine of essential natures is too discreet and lacks the explanatory power of views that emphasize external relations.’ Curran summarizes a form of this objection as follows:

The contemporary view sees reality more in terms of relations than of substances and natures. The individual is not thought of as a being totally constituted in the self, whose life is the unfolding of the nature already possessed . . . . According to a more contemporary, relational view, reality does not consist of separate substances completely independent of each other. Reality can be understood only in terms of the relations that exist among the individual beings.2 Regarding human flourishing, this view asserts that, The individual person has no intrinsic orientation (a nature) necessarily bringing about personal perfusion; rather, according to Aristotle, one depends more on the contingent and the accidental.3

These ‘contemporary theorists’ are correct that reality, taken as a whole, reflects relations among substances and not merely substances in isolation. Moreover, the human experience does indeed include contingency and accident. However, by acknowledging the role of accident and contingency, we must not deny or unnecessarily minimize the restrictive role of essential natures. The simple fact is that there are limits to the kind of change a human can undergo and still exist, as well as on the kinds of relations a human can sustain to other things. On our view, these limits establish parameters for every aspect of human development and personal flourishing. These facts are not only consistent with the doctrine of natures but also, best explained by that doctrine. Moreover, the doctrine of natures makes the best sense of the notions of contingency and accident by contrasting them to an enduring essence. Thus, one can assert that a thing is what it is and not another thing without ignoring contingent relations among existents, since the members of a given species possess a deeply unified and law-like structure that remains unaffected by contingency and accident. Essential natures, then, play an irreducibly crucial role in defining what a thing is, what it can become, and how it can be related to other entities.

A second objection centres on the entrenched debate in metaphysics over realism and nominalism. Against the typological view defended in this paper, some argue that ‘essence’ is a mere chimera, lacking empirical defence. J.M. Thoday suggests that genetic variations are so significant among members of any given population that regarding human beings, ‘there are as many human natures as there are men.’4 The obvious question for Thoday is why he refers to all men as having human natures? What is it that unifies this group of existents under the classification, ‘human’? He may respond that each human being has an individually distinct human nature, and thus may be grouped into the set we refer to as ‘humans’: (e.g., {Human Nature1, Human Nature2, Human Nature3 … Human Naturen}.)5 But this clearly does not solve the problem. For now the question is, what unifies the members of this set to warrant calling it the set of individual human natures? To avoid an infinite regress of individualized natures within natures or making exact similarity relations among them as primitives, we must eventually point to a universal human nature that allows us to refer to the unified group of existents we call humans. ‘…unless there is some tacit, generalizable understanding of what the word “human” means, some universal signification, then it could not be used to describe more than one organic entity.’6

While Thoday’s observation of genetic variance among populations is interesting, it hardly refutes the notion that essential natures are had and shared by members of a species. He is correct that identifying a single characteristic to fulfill this role may be difficult, but epistemic inability does not alter ontological reality. The essentialist case does not derive from our ability to catalogue and compare all the properties of existing species, finally identifying a peculiar trait in each, but rather, on the need to ground the unity of a naturally occurring class of entities. Moreover, the single-character taxonomy view is not a necessary component of essentialism. The essential nature of a being includes that set of peculiar properties and their internal relations that distinguish its class of membership from all others. The number of distinguishing characteristics in this set is irrelevant, as long as the set unifies the members of the species, irrespective of any accidental variances within the class. Thus, natural kind X will refer to all and only those beings who bear the essential X nature, regardless of any non-essential variations between the members of the class. This view is neither far fetched nor impractical.

A third argument against the essentialist view suggests that entering a species is a process. Speaking of the human species, Lawrence Becker asserts,

Human fetal development is a process analogous to metamorphosis, and just as it makes good sense to speak of butterfly eggs, larvae, and pupae as distinct from the butterflies they become (to say that they are not butterflies) so too it makes sense to say that human eggs, embryos, and fetuses are distinct from the human beings they become-that they are not human beings, only human becomings. When can we say that the fetus is a human being rather than a human becoming? Surely only when its metamorphic-like process is complete — that is, when the relatively undifferentiated mass of the fertilized human ovum has developed into the pattern of differentiated characteristic of the organism it is genetically programmed to become.7

Becker’s view is riddled with problems. First, he fails to distinguish between epistemic convention and essential natures. From the fact that we draw an epistemological distinction between ‘pupae,’ ‘larvae,’ and ‘butterfly,’ it does not follow that each is its own species, or that each is a different organism. Becker himself acknowledges that ‘caterpillars and butterflies are both stages in the same insect’.8 Though the former is modified morphologically into the latter, the essential nature of the one insect is identical in both cases. This is what allows us to justify the notion that these are different stages in the same organism. Likewise, though we distinguish between human new-borns and adults, it does not follow they are of different species, or are different organisms. Nor does it follow that because we distinguish between human fetuses and two year-old children, they belong to different species, or are different organisms. Thus, Becker’s distinction between human beings and human becomings is metaphysically confused. Moreover, he follows a widespread confusion that identifies a thing’s natural kind with an adult member of that kind. But as David Wiggins has shown, when we trace the laws of development for an organism, we ground this activity in a principle of individuation that is specific and that makes process and maturation intelligible.9

A second problem with Becker’s view is the suggestion that the fetus becomes a human being only after ‘its metamorphic-like process is complete … [when] … the relatively undifferentiated mass of the fertilized human ovum has developed into the pattern of differentiated characteristic of the organism . . . .’. This judgment is highly arbitrary, especially when applied to human beings, since the development process continues for decades after birth. Thus, it is difficult to see when Becker’s ‘metamorphic-like’ process is complete. Size and shape, as well as physical and mental capacities continue unfolding well into the teen-age years. Certainly the 18 year old is no more human than the 5 year old; but since the older person is further along in the (metamorphic) process, Becker’s distinction implies this conclusion. It seems apparent that both the child and the adult are equally human. This can be accounted for if both possess a common human nature. As mentioned earlier, this essential nature informs and directs the ‘metamorphic-like’ process throughout a human being’s life. Arguably, this same essential nature directs the process before birth. Nothing in Becker’s argument dissuades this suggestion.

Finally, Becker equivocates between human-becomings and human beings. All organisms, he claims, are ‘genetically programmed to become’ specifically differentiated entities. Presumably, this genetic programme allows the being to develop into its adult form. But what is this genetic programme if not an essential nature? How can it continue to direct an entity’s becoming if it does not continue to be present in that entity? Both the embryonic and adult stages of the organism possess the same genetic programme (nature). This unity of being allows Becker to refer to the fetus as the ‘it’ whose metamorphic process will one day be complete, affording ‘it’ the status of human being. On what basis, then, can Becker draw a metaphysical distinction between so-called human becomings and human beings? It seems none. Thus, he gives us no reason to doubt that the human embryo, possessing an identical genetic programme as the adult she will become, is a bona fide member of the human species.

Human Personhood and The Unborn

The following argument defends the humanity of the unborn.

  1. An adult human being is the end result of the continuous growth of the organism from conception.
  2. From conception to adulthood, there is no break in this development which is relevant to the ontological status of the organism.
  3. Therefore, one is a human being from the point of conception onward.10

Though few would deny premise 1, and premise 3 clearly follows from 1 and 2, the success of the argument rests on the truth of premise 2. In our view, premise 2 is as strong as premise 1. The fetus F, certainly seems to be a substance; an ontologically distinct organism, instantiating an essential nature. As such, F can and does undergo dramatic development and change, though remaining identical to itself as an individuated substance throughout the process. Further, since F belongs to the human species (instantiates an essentially human nature) at some point during the process, F must belong to the human species from the point of conception, since there is no ontologically significant break in the process (i.e., the same essential nature governs a single process from conception to adulthood). To deny that F is fully human from conception, one must point to an ontologically significant modification that occurs between conception and birth, and that would qualify as a substantial change. So far as we can tell, there is no good reason to believe that such a modification occurs at any point in the process (as opposed to important developmental moments within the life of one organism). Nevertheless, some have asserted ‘criteria for humanness,’ including morphology, quickening or spontaneous movement, viability, production of an EEC or birth to demarcate human beings from ‘potential’ human beings. Others, like Mary Ann Warren, draw a more sophisticated demarcation between so-called ‘genetic humanity’ and ‘moral humanity,’ claiming only those in the latter group are persons. Persons, she claims, must meet one of five criteria: 1. Consciousness… and in particular the ability to feel pain; 2. Reasoning, the developed capacity; 3. Self-motivated activity; 4. The capacity to communicate; 5. The presence of self-concepts.11 To this list, Joseph Fletcher adds a) self-control; b) a sense of the future and the past; c) the ability to relate to others; and d) curiosity.12 Similar to Warren’s ‘genetic/moral’ distinction, James Rachels draws a distinction between ‘biographical’ and ‘biological’ life,13 placing the emphasis on the possession of low order capacities that constitute the former. We will consider each of these in turn.

Morphology and quickening are unhelpful criteria, since they confuse metaphysics with epistemology by inferring that essence is a function of outside observation. Moreover, Werner rightly dismisses these criteria by pointing to grossly deformed and fully paralyzed adult human beings. If these individuals are human persons, this determination rests on some criterion other than morphology or spontaneous movement. Likewise, viability is clearly a non-starter, since it relegates human personhood to a function of medical technology. Similarly, birth is a wholly arbitrary, metaphysically irrelevant criterion, since ontology is not a function of venue. We are left, then, with the EEG criterion and the more sophisticated criteria of Werner, Fletcher and Rachels.

What about the EEG requirement? Apart from its prima facie appeal, this criterion fails for two reasons. First, while it is true that a thing functions in light of what it is, a thing is what it is, not what it does. From the fact that an embryo does not have a recordable EEG, it does not follow that the embryo is not human. An equally logical conclusion is that possessing a recordable EEG is not one of its first order capacities at that particular stage in its existence. The same could be said of the capacity to master quantum physics. Disappointingly, this may not be a first-order capacity in one’s life. Nevertheless, in such a case, it is still a higher order (unexpressed) capacity. Though some of one’s capacities are yet unexpressed, it hardly follows that the individual is other than human. Both our first and second-order capacities are grounded in the ultimate capacities that constitute our essential human nature. This reality is clearly evident when we consider that it is entirely possible for an adult human’s EEG to cease (at least to be measurable), only to begin again a short time later. If the EEG criterion is applied consistently, such an individual would be momentarily a non-human person and then regain her human personhood a short time later, but this is a strained and unnecessary view of what is going on. Adding qualifications like, ‘a human being is one who has been a human being before and will have an EEG in the future’ fail as well. Werner comments,

Besides the fact that the addition of the clause, one has been a human being before’ seems totally ad hoc (the function it serves is to rule out embryos and fetuses as humans), [it] also has some rather undesirable consequences. For instance, if a doctor were working to revive the EEG of a patient and someone came into the room and shot the patient in the head, we could not say that the patient, qua human being, was killed by the gunshot wound. Since the patient neither had an EEC nor would have one in the future, he would, by this criterion, have ceased to be a human being prior to the time of the gun shot.14

The more sophisticated criteria asserted by Warren, Fletcher and Rachels fare no better than those above. While epistemically thought-provoking, all functional criteria for personhood fail to draw a convincing, ontological distinction between born and unborn human beings. Moreover, they seem arbitrary, metaphysically inadequate and ethically problematic. In our view, the entire project of defining personhood in functional terms fails, since, as argued above, a thing is what it is, not what it does. Moreover, the absence of lower order functional capacities does not mean that the individual’s ultimate capacities for those lower abilities are absent. In general, a thing’s highest order capacities are realized through the development of a structural hierarchy of capacities under them. In fact, the very notion of a functional defect or privation would seem to presuppose this archetypical perspective. Thus, the absence of a lower order capacity merely signals the fact that a higher order capacity cannot be realized; it does not indicate the absence of the latter. Applied to the unborn, from the assertion that the unborn, defective or otherwise, may15 be incapable of first-order human person skills like reasoning, communication, willing, desiring, self-reflection, aspiring, etc., it does not follow that they are not human persons. For these capacities still exist within the individual human substance as ultimate capacities constituting its essence. Therefore, even if these criteria were among the legitimate epistemological identifiers of personhood, every human substance, born and unborn would qualify as a human person; for a human being is a substance with all the ultimate capacities for fully expressed personhood, including those listed by Warren, Fletcher and Rachels.

The ontological inadequacies of functional definitions become evident if we try to practise them consistently. Applying any of the above criteria, counter-intuitive and ethically troubling results abound. Consider the person under general anesthesia. He is clearly not conscious, has no expressed capacity for reason, is incapable of self-motivated activity, cannot possibly communicate, has no concept of himself, and cannot remember the past or aspire for the future. According to the functionalist view, he is not a full person-but this is absurd. In response, it may be argued that the adult lacks the first-order capacity to respond, but still has the capacity to exercise the first-order capacity when free from anesthesia and is therefore a person who is temporarily dysfunctional. But this ad hoc claim is not available without appealing to something outside of first-order functional criteria. Appealing to unexpressed but higher order capacities as evidence of personhood smacks of essentialism; that is, defending the personhood of the anesthetized human seems to require pointing to higher order capacities embedded in human nature. To argue that the person before anesthesia remains a person while under anesthesia, we must point to what that person is, irrespective of the functioning of first-order capacities, not what the person is doing. To insist that he remains a person because he had once expressed first order-capacities of consciousness begs the question, since this merely reasserts the functional premise as a defence against the counter-argument.

A final consequence of the functionalist view takes us back to the problem with Becker’s ‘human-becomings’. Specifically, if essential personhood is determined by function, it follows that essential personhood is a degreed property. After all, some will realize more of their capacities to reason, feel pain, self-reflect, etc., than others. Moreover, it is undeniable that the first several years of normal life outside the womb include increasing expression of human capacities. Likewise, the last several years of life include decreasingly expressed human capacities. Consequently, if the functionalist view is correct, the possession of personhood could be expressed by a bell-curve, in which a human being moves toward full personhood in her first year of life, reaches full personhood at a given point, and then gradually loses her personhood until the end of her life. Presumably, the commensurate rights of persons would increase, stabilize and decrease in the process. Without appealing to something other than function, it is difficult to resist this counter-intuitive conclusion. Indeed, intellectual honesty has driven many to embrace this end, and the slope is ever so slippery. Applying functional reasoning to infanticide, Kuhse and Singer comment on the ontological status of newborns:

… When we kill a newborn, there is no person whose life is begun. When I think of myself as the person I am now, I realize that I did not come into existence until sometime after my birth … It is the beginning of the life of the person, rather than of the physical organism, that is crucial so far as the right to life is concerned.16

While we applaud their intellectual consistency in applying their notion of personhood evenly in ethical issues, their chilling consistency reveals, at least to us, the danger of defining human personhood in functional terms. Not only are the unborn and newborns less than persons, apparently all of us are subject to graded personhood and the commensurate rights therein. This conclusion seems unavoidable given a functional view of personhood.

It could be responded that the criteria for personhood pick out degreed properties that are, at the same time, threshold properties, i.e., properties that either have or have not made an appearance and that, once exemplified, they are degreed to the extent to which they are developed. According to this response, it is the presence or absence of the threshold property, not the degree of development, that is of relevance to moral value. But this response seems to be inadequate. The intrinsic value is either the individual human person that has the functional properties or the presence of those properties themselves. If the latter, it is hard to see what is so important about the mere presence of a property of personhood since the worth of these features varies with the degree of their realization. All things being equal, having more rational abilities is more valuable than having a minimalistic form of rationality. If the former, then it is the human person himself or herself who is of value. But then, as we have argued, there is no good reason to think the person pops into existence the moment certain threshold properties are exemplified. Instead, the human person is the bearer of the ultimate capacities for these to be actualized. And if advocates of this lemma allow a human person’s value to remain constant irrespective of the degree to which the properties of personhood are realized, there is no reason not to press the point further and apply it to the value of the human person prior to but with the ultimate capacity for the instancing of these threshold properties.

In this paper, we have argued that to be a human person is to possess an essential human nature, The unborn are individual human substances, possessing an essentially human nature; therefore, they are human persons. Functional definitions of personhood are arbitrary, metaphysically inadequate and ethically problematic. Metaphysical insight prompts us to remember that a thing is what it is, not what it does. Essence precedes function-to possess an essential human nature is to be a human person, regardless of what the story is regarding first-order capacities.


  1. See W.V. Quine, Ontological Relativity and Other Essays (New York: Columbia University Press, 1969) for an explication of this view.
  2. Charles E, Curran, ‘Natural Law in Moral Theology,’ Readings in Moral Theology No. 7: Natural Law and Theology. (New York: Paulist, 1991), 276.
  3. Ibid., 277.
  4. J.M. Thoday, ‘Geneticism and Environmentalism,’ J.E. Meade and AS. Parker eds., Biological Aspects of Social Problems (Edinburgh: Oliver Boyd, 1965), 101. As quoted Daniel Callahan, ‘The “Beginning” of Human Life,’ Michael F. Goodman, ed., What is a person (New Jersey: Humana Press, 1988), 41.
  5. For a detailed defence of metaphysical realism, see Reinhardt Grossman, The Existence of The World: An Introduction to Ontology (New Jersey: Humana Press, 1988), 41.
  6. ?
  7. Lawrence Becker, ‘Human Being: The Boundaries of the Concept, Michael F. Goodman, ed., What is a Person (New Jersey: Humana Press, 1988), 60.
  8. Ibid., 60.
  9. David Wiggins, Sameness and Substance (Cambridge, Mass.: Harvard University Press, 1980).
  10. cf. Richard Werner, ‘Abortion: The Moral status of the Unborn,’ Social Theory and Practice, vol. 4, (Spring 1975): 201-222.
  11. Mary Ann Warren, ‘On the Moral and Legal Status of Abortion,’ James A. Sterba, ed., Morality In Practice (Hardford: Wadsworth), 144-145. Quoted by W.F. Cooney, ‘The fallacy of All Person-Denying Arguments for Abortion,’ Journal of Applied Philosophy vol. 8, no. 2 (1991): 163.
  12. Joseph Fletcher, ‘Indicators of Humanhood: A Tentative Profile,’ Hastings Center Report, vol. 2 (1972). Quoted by Scott Rae, ‘Views of Human Nature at The Edges of Life,’ Christian Perspectives on Being Human: An Integrative Approach (Grand Rapids: Baker, 1993), 239.
  13. James Rachels, The End of Life. (New York: Oxford Press, 1987), 5.
  14. Ibid., 203.
  15. Much of this argument boils down to epistemological, not metaphysical issues. Our ability to reliably ascertain the functional abilities of the unborn is hardly exhaustive. The budding field of prenatal psychology, experimental it may be, points to the fact that much of the cognitive/self-awareness capabilities of the unborn remain unexplored.
  16. Kuhse and Singer, Should the Baby Live (New York: Oxford Press, 1985), 133. It is quickly apparent that Kuhse and Singer equivocate on the question of personal identity. After all, if I do not exist until sometime after my birth, in what sense is the birth mine? The only way for ‘my birth’ to be more than a linguistic convention is to admit that ‘I’ existed before I was born, or at least at the time of my birth. If this is the case, Kuhse and Singer’s attempt to define personhood in terms of function fails.