Article ID: DA020-3 | By: Francis J. Beckwith

This article first appeared in the CHRISTIAN RESEARCH JOURNAL, Spring (1991). The full text of this article in PDF format can be obtained by clicking here. For further information or to subscribe to the CHRISTIAN RESEARCH JOURNAL, go to:

Throughout the history of the abortion controversy, many have put forth criteria by which to judge whether a human organism has reached the point in its development at which it is fully human. Some criteria are based on so-called “decisive” moments in fetal development. Others are based on certain conditions any entity — born or unborn — must fulfill in order to be considered “fully human.” And others argue that there is no “decisive” moment but that the unborn’s rights increase as its body develops. I believe that all these views are flawed. I will argue that the pro-life view that full humanness begins at conception is the most coherent and is more consistent with our basic moral intuitions. In order to defend this position adequately, I will — both in this article and in the final installment of this series — critique a number of decisive moment and gradualist theories, whose defenses contain many objections to the pro-life view.

Agnostic Approach: “No One Knows When Life Begins”

It is often claimed by abortion-rights advocates that “no one knows when life begins.” Right away it must be observed that this formulation is imprecise. For no one who knows anything about prenatal development seriously doubts that individual biological human life is present from conception (see above). What the abortion-rights advocates probably mean when they say that “no one knows when life begins” is that no one knows when full humanness is attained in the process of human development by the individual in the womb. Thus, from a legal perspective they are arguing: since no one knows when full humanness is attained, abortion should remain legal. I believe, however, that there are at least four problems with this argument. (1) It is a two-edged sword. If no one knows when full humanness is attained, then we cannot prevent a Satan-worshipping neighbor, who believes that full humanness begins at the age of two, from sacrificing his one-and-a-half-year-old son to the unholy one. After all, who knows when life begins? (2) If it is true that we don’t know when full humanness begins, this is an excellent reason not to kill the unborn, since we may be killing a human entity who has a full right to life. If game hunters shot at rustling bushes with this same philosophical mind-set, the National Rifle Association’s membership would become severely depleted. Ignorance of a being’s status is certainly not justification for killing it. (3) As the above biological facts of prenatal development indicate, we have excellent reason to believe that full humanness is present from the moment of conception, and that the nature of prenatal and postuterine existence is merely the unfolding of human growth and development which does not cease until death. In other words, the unborn — like the rest of us — are not potential human beings, but human beings with much potential. (4) By permitting abortion for virtually any reason during the entire nine months of pregnancy, abortion-rights advocates have decided, for all practical purposes, when full humanness is attained. They have decided that this moment occurs at birth, although some of them — such as Peter Singer and Michael Tooley — also advocate infanticide.8 The very abortion-rights advocates who claim that “no one knows when life begins” often act as if protectable human life begins at birth. Since actions speak louder than words, these “pro-choicers” are not telling the truth when they claim they “don’t know when life begins.” Some abortion-rights literature, which I am certain is quite embarrassing to the more sophisticated proponents of this cause, claims that “personhood at conception is a religious belief, not a provable biological fact.”9 What could possibly be meant by this assertion? Is it claiming that religious claims are in principle unprovable scientifically? If it is, it is incorrect — for many religions, such as Christianity and Islam, believe that the physical world literally exists, which is a major assumption of contemporary science. On the other hand, some religions, such as Christian Science and certain forms of Hinduism,10 deny the literal existence of the physical world. But maybe this “pro-choice” assertion is simply claiming that biology can tell us nothing about values. If this is what is meant, it is right in one sense and wrong in another. It is right if it means that the physical facts of science, without any moral reflection on our part, cannot tell us what is right and wrong. But it is wrong if it means that the physical facts of science cannot tell us to whom we should apply the values of which we are already aware. For example, if I don’t know whether the object I am driving toward in my car is a living woman, a female corpse, or a mannequin, biology is extremely important in helping me to avoid committing an act of homicide. Running over mannequins and corpses is not homicide, but running over a living woman is. Maybe the “pro-choice” assertion is saying that when human life should be valued is a philosophical belief that cannot be proven scientifically. Maybe so, but this cuts both ways. For isn’t the belief that a woman has abortion rights a philosophical belief that cannot be proven scientifically and over which people obviously disagree? But if the pro-life position cannot be enacted into law because it is philosophical (or religious), then neither can the abortion-rights position. Now the abortion-rights advocate may respond to this by saying that this fact alone is a good reason to leave it up to each individual woman to choose whether she should have an abortion. But this response begs the question, for this is precisely the abortion-rights position. Furthermore, the pro-lifer could reply to this abortion-rights response by employing the pro-choicer’s own logic. The pro-lifer could argue that since the abortion-rights position is a philosophical position over which many people disagree, we should permit each individual unborn human being to be born and make up his or her own mind as to whether he or she should or should not die. In sum, it seems that the appeal to ignorance is seriously flawed.


There are some pro-life advocates, such as Dr. Bernard Nathanson,11 who argue that full humanness begins when the conceptus is implanted in its mother’s womb, which occurs within one week after conception. There are four basic arguments for this position to which I will respond. (1) Nathanson argues that at the moment of implantation the unborn “establishes its presence to the rest of us by transmitting its own signals — by producing hormones — approximately one week after fertilization and as soon as it burrows into the alien uterine wall.” For Nathanson implantation is significant because prior to this time the unborn “has the genetic structure but is incomplete, lacking the essential element that produces life: an interface with the human community and communication of the fact that it is there.”12 So, for Nathanson the unborn’s hormonal communication to its mother is essential for humanness. I believe that this argument is flawed for at least two important reasons. First, how is it possible that one’s essence is dependent on whether others are aware of one’s existence? It seems intuitively correct to say that it is not essential to your being whether or not anyone knows you exist, for you are who you are regardless of whether others are aware of your existence. One interacts with a human being, one does not make a being human by interacting with it. In philosophical terms, Nathanson is confusing epistemology (the study of how we know things) with ontology (the study of being or existence). A second objection, which supports my first objection, is mentioned by Nathanson himself. He writes, “If implantation is biologically the decisive point for alpha’s [the unborn’s] existence, what do we do about the ‘test-tube’ conceptions? The zygote in these cases is seen in its culture dish and could be said to announce its existence even before it is implanted.” Nathanson responds to these questions by asserting, “It seems to me that when it is in the dish the zygote is already implanted, philosophically and biochemically, and has established the nexus with the human community, before it is ‘re’-implanted into the mother’s womb.”13 This response, however, does not support Nathanson’s position, for he is admitting that there is no real essential difference between the implanted and the nonimplanted zygote, just an accidental difference (the former’s existence is known while the latter’s is not). Hence, just as there is no essential difference between a Donald Trump who is an unknown hermit and a Donald Trump who is an entrepreneur and billionaire (there are only accidental differences between the two Trumps), there is no essential difference between an unknown conceptus and a known conceptus. In sum, it seems counterintuitive to assert that one’s essence is dependent on another’s knowledge of one’s existence. (2) There is a second argument for implantation as the decisive moment: If we say that full humanness begins at conception, we must respond to the observation that “some entities that stem from the union of sperm and egg are not ‘human beings’ and never will develop into them,” and that there may be some human beings who come into being without the union of sperm and egg.14 Concerning the former, Nathanson gives examples of nonhuman entities that result from the sperm-egg union: the hydatidiform mole (“an entity which is usually just a degenerated placenta and typically has a random number of chromosomes”), the choriocarcinoma (“a ‘conception-cancer’ resulting from the sperm-egg union is one of gynecology’s most malignant tumors”), and the blighted ovum (“a conception with the forty-six chromosomes but which is only a placenta, lacks an embryonic plate, and is always aborted naturally after implantation”). Concerning the latter, a clone is an example of a human entity that may come into being without benefit of a sperm-egg union.15 The problem with Nathanson’s argument is that he confuses necessary and sufficient conditions. One who holds that full humanness begins at conception is not arguing that everything which results from the sperm-egg union is necessarily a conception. That is, every conception of a unique individual human entity is the result of a sperm-egg union, but not every sperm-egg union results in such a conception. Hence, the sperm-egg union is a necessary condition for conception, but not a sufficient condition. Furthermore, Nathanson is correct in asserting that it is possible that some day there may be human beings, such as clones, who come into existence without benefit of conception.16 But this would only mean that conception is not a necessary condition for full humanness, just as the sperm-egg union is not a sufficient condition for conception. In sum, Nathanson’s argument from both nonhuman products of sperm-egg unions and the possibility of clones is inadequate in overturning the pro-life position that full humanness begins at conception. (3) It is estimated that twenty to fifty percent of all conceptions die before birth. Thirty percent, it is estimated, die before implantation.17 Some people argue that these facts make it difficult to believe that the unborn are fully human in at least the very earliest stage of their development prior to implantation. But this is clearly an invalid argument, for it does not logically follow from the number of unborn entities who die that these entities are not by nature fully human. To cite an example, it does not follow from the fact that underdeveloped countries have a high infant mortality rate that their babies are less human than those born in countries with a low infant mortality rate. Suppose the pro-choice advocate responds to this by arguing that if every fertilized ovum is human, then we are obligated to save all spontaneous abortions as well. But if we did, it would lead to overpopulation, death by medical neglect, and starvation. The problem with this response is that it confuses our obvious prima facie moral obligation not to commit homicide (that is, to perform an abortion) with the questionable moral obligation to interfere with natural death (that is, to permit the conceptus to abort spontaneously). “Protecting life is a moral obligation, but resisting natural death is not necessarily a moral duty…There is no inconsistency between preserving natural life, opposing artificial abortion and allowing natural death by spontaneous abortion.”18 Admittedly, the question of interference in spontaneous abortions provokes the pro-life ethicist to think more deeply and sensitively about his or her position and to make distinctions and nuances that may not be pleasing to all who call themselves pro-life. But just as the difficult question of whether to pull the plug on the irreversibly comatose who are machine-dependent does not count against the position that murdering healthy adults is morally wrong, the question of how we should ethically respond to spontaneous abortions does not count against the pro-life ethic which says that we should not directly kill the healthy and normally developing unborn. (4) Some people argue that since both twinning (the division of a single conceptus) and recombination (the reuniting of two concepti) occur prior to implantation, individual human life does not begin until that time. However, a careful examination of the nature of twinning and recombination reveals that there is no reason to suppose that the original pre-twinned conceptus or any pre-recombined conceptus was not fully human. First, scientists are not agreed on many aspects of twinning. Some claim that twinning may be a nonsexual form of parthenogenesis or “parenting.” This occurs in some animals and plants. Others claim that when twinning occurs, an existing human being dies and gives life to two new and identical human beings like himself or herself. Still others claim that since not all human concepti have the capacity to twin, one could argue that there exists in some concepti a basic duality prior to the split. Hence, it may be claimed that at least in some incipient form two individual lives were present from the start at conception. In any event, the fact of twinning does not seem to be a sufficient reason to give up the belief that full humanness begins at conception.19 Second, every conceptus, whether before twinning or recombination, is still a genetically unique individual who is distinct from his or her parents. In other words, if identical twins result from a conceptus split or one individual results from two concepti that recombine, it does not logically follow that any of the concepti prior to twinning or recombining were not human.20 To help us understand this point, philosopher Robert Wennberg provides the following story:

Imagine that we lived in a world in which a certain small percentage of teenagers replicated themselves by some mysterious natural means, splitting in two upon reaching their sixteenth birthday. We would not in the least be inclined to conclude that no human being could therefore be considered a person prior to becoming sixteen years of age; nor would we conclude that life could be taken with greater impunity prior to replication than afterward. The real oddity — to press the parallel — would be two teenagers becoming one. However, in all of this we still would not judge the individual’s claim to life to be undermined in any way. We might puzzle over questions of personal identity… but we would not allow these strange replications and fusions to influence our thinking about an individual’s right to life. Nor therefore does it seem that such considerations are relevant in determining the point at which an individual might assume a right to life in utero.21

The Appearance of “Humanness”

Some argue that the unborn becomes fully human at the time at which it begins to take on the appearance of a child. Professor Ernest Van Den Haag22 is sympathetic to this criterion, though he combines it with the criterion of sentience which I will deal with below. He writes that when the unborn acquires a functioning brain and neural system soon after the first trimester (though brain waves can be detected at 40 to 42 days after conception, which Van Den Haag does not mention), it “starts to resemble an embryonic human being.” After this point “abortion seems justifiable only by the gravest of reasons, such as the danger to the mother; for what is being aborted undeniably resembles a human being to an uncomfortable degree.”23 There are several problems with this argument. First, though appearance can be helpful in determining what is or is not fully human, it is not a sufficient or a necessary condition for doing so. After all, mannequins in stores resemble humans and they are not even remotely human. On the other hand, some human oddities — such as the bearded lady or the elephant man, who more closely resemble nonhuman primates — are nonetheless fully human. The reason why we believe that the bearded lady and the elephant man are fully human and the mannequin is not is because the former are functioning individual organisms that genetically belong to the species homo sapiens. The latter is an inanimate object. Second, Davis points out that “this objection assumes that personhood presupposes a postnatal form. A little reflection, however, will show that the concept of a ‘human form’ is a dynamic and not a static one. Each of us, during normal growth and development, exhibits a long succession of different outward forms.” An early embryo, though not looking like a newborn, does look exactly like a human ought to look at this stage of his or her development. Thus, “the appearance of an 80-year-old adult differs greatly from that of a newborn child, and yet we speak without hesitation of both as persons. In both cases, we have learned to recognize the physical appearances associated with those development stages as normal expressions of human personhood.”24 It may be true that it is psychologically easier to kill something that does not resemble the human beings we see in everyday life, but it does not follow from this that the being in question is any less human or that the executioner is any more humane. Once we recognize that human development is a process that does not cease at the time of birth, then “to insist that the unborn at six weeks look like the newborn infant is no more reasonable than to expect the newborn to look like a teenager. If we acknowledge as ‘human’ a succession of outward forms after birth, there is no reason not to extend that courtesy to the unborn, since human life is a continuum from conception to natural death.”25 Hence, Van Den Haag, by confusing appearance with reality, may have inadvertently created a new prejudice, “natalism.” And, like other prejudices such as sexism and racism, natalism emphasizes nonessential differences (“they have a different appearance”) in order to support a favored group (“the already born”).

Human Sentiment

Some pro-choice people argue that since parents do not grieve at the death of an embryo or fetus as they would at the death of an infant, the unborn are not fully human. As a standard for moral action, this criterion rests on a very unstable foundation. As Noonan has observed, “Feeling is notoriously an unsure guide to the humanity of others. Many groups of humans have had difficulty in feeling that persons of another tongue, color, religion, sex, are as human as they.”26 One usually feels a greater sense of loss at the sudden death of a healthy parent than one feels for the hundreds who die daily of starvation in underdeveloped countries. Does this mean that the latter are less human than one’s parent? Certainly not. Noonan points out that “apart from reactions to alien groups, we mourn the loss of a ten-year-old boy more than the loss of his one-day-old brother or his 90-year-old grandfather.” The reason for this is that “the difference felt and the grief expressed vary with the potentialities extinguished, or the experience wiped out; they do not seem to point to any substantial difference in the humanity of baby, boy, or grandfather.”27


Quickening has traditionally referred to the first movement of the unborn felt by her mother. It was at this time in fetal development that some ancient, medieval and common-law scholars thought it could be proved that the unborn was “alive” or that the soul had entered her body. Not having access to the biological facts we currently possess, they reasoned that prior to quickening it could not be proved that the unborn entity was “alive” or fully human. Current biology, which has conclusively demonstrated that a biologically living human individual is present from conception, has decisively refuted this notion of “quickening,” just as current astronomy has refuted the geocentric solar system. Now, does this mean that our ancestors were not pro-life? Not at all. Legal scholar and theologian John Warwick Montgomery notes that when our ancient, medieval, and common-law forefathers talked about quickening as the beginning of life, “they were just identifying the first evidence of life they could conclusively detect…They were saying that as soon as you had life, there must be protection. Now we know that life starts at the moment of conception with nothing superadded.”28 Hence, to be consistent with contemporary science, legal protection must be extended to the unborn entity from the moment of conception. Furthermore, we now know that the ability to feel the unborn’s movement is contingent upon the amount of the mother’s body fat. It seems silly to say that one’s preborn humanness is contingent upon whether one is fortunate to have been conceived in a body that frequents aerobics classes.


Some people argue that birth is the time the human entity becomes fully human. They usually hold this position for two reasons: (1) our society calculates the beginning of one’s existence from one’s day of birth; and (2) it is only after birth that a child is named, baptized, and accepted into a family. This argument is subject to several criticisms. First, that our society counts one’s beginning from one’s birthday and that people name and baptize children after their births are simply social conventions. One is not less human if one is abandoned, unnamed, and not baptized. Some cultures, such as the Chinese, count one’s beginning from the moment of conception. Does that mean that the American unborn are not fully human while the Chinese unborn are? Second, there is no essential difference between an unborn entity and a newborn baby, just a difference in location. As Wennberg writes, “surely personhood and the right to life is not a matter of location. It should be what you are, not where you are that determines whether you have a right to life.”29 In fact, abortion-rights philosophers Peter Singer and Helga Kuhse write, “The pro-life groups are right about one thing: the location of the baby inside or outside the womb cannot make such a crucial moral difference. We cannot coherently hold that it is all right to kill a fetus a week before birth, but as soon as the baby is born everything must be done to keep it alive.”30 Third, as Wennberg points out, a newborn chimpanzee can be treated like a human newborn (i.e., named, baptized, accepted into a family), but this does not mean that it is fully human.31


  1. The facts in this section are taken from the following: F. Beck, D. B. Moffat, and D. P. Davies, Human Embryology, 2d ed. (Oxford: Basil Blackwell, 1985); Keith L. Moore, The Developing Human: Clinically Oriented Embryology, 2d ed. (Philadelphia: W. B. Saunders, 1977); Andre E. Hellegers, “Fetal Development,” in Biomedical Ethics, ed. Thomas A. Mappes and Jane S. Zembaty (New York: Macmillan, 1981), 405-9; and Stephen M. Krason, Abortion: Politics, Morality, and the Constitution (Lanham, MD: University Press of America, 1984), 337-49.
  2. Subcommittee on Separation of Powers, report to Senate Judiciary Committee S-158, 97th Congress, 1st Session, 1981, as quoted in Norman L. Geisler, Christian Ethics: Options and Issues (Grand Rapids: Baker, 1989), 149.
  3. James J. Diamond, M.D., “Abortion, Animation and Biological Hominization,” Theological Studies 36 (June 1975): 305-42.
  4. Krason, 341.
  5. John T. Noonan, “The Experience of Pain by the Unborn,” in The Zero People, ed. Jeff Lane Hensley (Ann Arbor, MI: Servant, 1983), 141-56.
  6. Ibid., 151-52.
  7. See Mortimer Rosen, “The Secret Brain: Learning Before Birth,” Harper’s, April 1978, 46-47.
  8. See Michael Tooley, Abortion and Infanticide (Oxford: Clarendon Press, 1983); and Peter Singer and Helga Kuhse, “On Letting Handicapped Infants Die,” in The Right Thing to Do, ed. James Rachels (New York: Random House, 1989).
  9. This is from a pamphlet distributed by the National Abortion Rights Action League, Choice Legal Abortion: Abortion Pro & Con, prepared by Polly Rothstein and Marian Williams (White Plains, NY: Westchester Coalition for Legal Abortion, 1983), n.p.
  10. On Christian Science, see Walter R. Martin, Kingdom of the Cults, 2d rev. ed. (Minneapolis: Bethany House, 1977), 111-46. On the Hindu denial of the physical world, see Elliot Miller, A Crash Course on the New Age Movement (Grand Rapids: Baker, 1989), 16-18, 22.
  11. Bernard Nathanson, M.D., Aborting America (New York: Doubleday, 1979), 213-17.
  12. Ibid., 216.
  13. Ibid., 217.
  14. Ibid., 214.
  15. Ibid.
  16. For a summary of the philosophical and scientific problems surrounding human cloning, see Andrew Varga, The Main Issues in Bioethics, 2d. ed. (New York: Paulist Press, 1984), 119-26.
  17. As cited in John Jefferson Davis, Abortion and the Christian (Phillipsburg, NJ: Presbyterian and Reformed, 1984), 60. Cf. Thomas W. Hilgers, M.D., “Human Reproduction,” Theological Studies 38 (1977):136-52.
  18. Geisler, Christian Ethics, 153.
  19. See Varga, 64-65.
  20. Ibid., 65.
  21. Robert Wennberg, Life in the Balance: Exploring the Abortion Controversy (Grand Rapids: William B. Eerdmans Publishing Co., 1985), 71.
  22. Ernest Van Den Haag, “Is There a Middle Ground?”, National Review, 12 December 1989, 29-31.
  23. Ibid., 30.
  24. Davis, 58.
  25. Ibid., 59.
  26. John T. Noonan, “An Almost Absolute Value in History,” in The Morality of Abortion, ed. and intro. John T. Noonan (Cambridge, MA: Harvard University Press, 1970), 53.
  27. Ibid.
  28. John Warwick Montgomery, Slaughter of the Innocents (Westchester, IL: Crossway, 1981), 37. For more on quickening, see ibid., 103-19; and David W. Louisell and John T. Noonan, “Constitutional Balance,” in The Morality of Abortion, 223-26.
  29. Wennberg, Life in the Balance, 77.
  30. Singer and Kuhse, 146.
  31. Wennberg, 77-78.