Realizing that many popular arguments for abortion rights — such as some of the ones found in the first two installments in this series — have little logical merit, many philosophers, ethicists, and theologians have presented more sophisticated arguments for abortion rights. These radical and moderate pro-choice thinkers agree with pro-life advocates that the abortion debate rests on the moral status of the unborn: if the unborn are fully human, then nearly every abortion performed is tantamount to murder. They argue, however, that although the unborn entity is human, insofar as belonging to the species homo sapiens, it is not a person and hence not fully human.
Those who argue in this fashion defend either a decisive moment or gradualist approach to the status of the unborn. Those who defend a decisive moment view argue that, although human life does begin at the moment of conception, it is at some later stage in the unborn human’s development that it becomes worthy of our protection. It is at this moment that it becomes a person.
Other philosophers take a gradualist position and argue that the unborn human gradually gains more rights as it develops. Hence, a zygote has less rights than a 6-month-old fetus, but this fetus has less rights than an adult woman.
In order to understand decisive moment and gradualist theories, it is important that we carefully go over the biological facts of fetal development. In this third installment of my four-part series I will cover the facts of fetal development and some decisive moment theories. In Part Four I will critique some more decisive moment theories and the gradualist view, concluding with responses to common questions asked about the pro-life view that full humanness begins at conception.
LIFE BEGINNING AT CONCEPTION AND THE FACTS OF PRE-NATAL DEVELOPMENT 
While going over the facts of prenatal development I will present the case for the pro-life view that full humanness begins at conception. I will deal with objections to this view when I critique the decisive moment and gradualist views in both this article and the final part of this series.
Pregnancy begins at conception, the time at which the male sperm and the female ovum unite. What results is called a zygote, a one-celled biological entity, a stage in human development through which each of us has passed (just as we have passed through infancy, childhood, and adolescence). It is a misnomer to refer to this entity as a “fertilized ovum.” For both ovum and sperm, which are genetically each a part of its owner (mother and father, respectively), cease to exist at the moment of conception. There is no doubt that the zygote is biologically alive. It fulfills the four criteria needed to establish biological life: (1) metabolism, (2) growth, (3) reaction to stimuli, and (4) reproduction. (There is cell reproduction and twinning, a form of asexual reproduction, which can occur after conception. For more on twinning, see below.) But is this life fully human? I believe that the facts clearly reveal that it is.
First, the human conceptus — that which results from conception and begins as a zygote — is the sexual product of human parents. Hence, insofar as having human causes, the conceptus is human.
Second, not only is the conceptus human insofar as being caused by humans, it is a unique human individual, just as each of us is. Resulting from the union of the female ovum (which contains 23 chromosomes) and the male sperm (which contains 23 chromosomes), the conceptus is a new — although tiny — individual. It has its own unique genetic code (with forty-six chromosomes), which is neither the mother’s nor the father’s. From this point until death, no new genetic information is needed to make the unborn entity a unique individual human. Her (or his) genetic make-up is established at conception, determining her unique individual physical characteristics — gender, eye color, bone structure, hair color, skin color, susceptibility to certain diseases, etc. That is to say, at conception, the “genotype” — the inherited characteristics of a unique human being — is established and will remain in force for the entire life of this individual. Although sharing the same nature with all human beings, the unborn individual, like each one of us, is unlike any that has been conceived before and unlike any that will ever be conceived again. The only thing necessary for the growth and development of this human organism (as with the rest of us) is oxygen, food, and water, since this organism — like the newborn, the infant, and the adolescent — needs only to develop in accordance with her already-designed nature that is present at conception.
This is why French geneticist Jermoe L. LeJeune, while testifying before a Senate Subcommittee, asserted: “To accept the fact that after fertilization has taken place a new human has come into being is no longer a matter of taste or opinion. The human nature of the human being from conception to old age is not a metaphysical contention, it is plain experimental evidence.” 
There is hence no doubt that the development of a unique individual human life begins at conception. It is vital that you — the reader — understand that you did not come from a zygote, you once were a zygote; you did not come from an embryo, you once were an embryo; you did not come from a fetus, you once were a fetus; you did not come from an adolescent, you once were an adolescent. Consequently, each one of us has experienced these various developmental stages of life. None of these stages, however, imparted to us our humanity.
Within one week after conception, implantation occurs — the time at which the conceptus “nests” or implants in her mother’s uterus. During this time, and possibly up to fourteen days after conception,  a splitting of the conceptus may occur resulting in the creation of identical twins. In some instances the two concepti may recombine and become one conceptus. (I will respond below to the argument that the possibility of the conceptus twinning and the subsequent concepti recombining refutes the pro-life claim that full humanness begins at conception.) At about three weeks, a primitive heart muscle begins to pulsate. Other organs begin to develop during the first month, such as a liver, primitive kidneys, a digestive tract, and a simple umbilical cord. This developing body has a head and a developing face with primitive ears, mouth, and eyes, despite the fact that it is no larger than half the size of a pea. Toward the end of the first month (between 26 and 28 days) the arms and legs begin to appear as tiny buds. A whole embryo is formed by the end of the first month.
From the eighteenth day after conception, substantial development of the brain and nervous system occurs.
- This is necessary because the nervous system integrates the action of all the other systems. By the end of the twentieth day the foundation of the child’s brain, spinal cord, and entire nervous system will have been established. By the sixth week, this system will have developed so well that it is controlling movements of the baby’s muscles, even though the woman may not be aware she is pregnant. At thirty days the primary brain is seen. By the thirty-third day the cerebral cortex, the part of the central nervous system which governs motor activity as well as intellect, may be seen. 
Despite its small size, the unborn child by the beginning of the second month looks distinctly “human” (although — as this article maintains — it is human from conception). At this point it is highly likely that the mother does not even know she is pregnant. Brain waves can be detected in the unborn at about forty to forty-three days after conception. During the second month, the eyes, ears, nose, toes, and fingers make their appearance; the skeleton develops; the heart beats; and the blood — with its own type — flows. The unborn at this time has reflexes and her lips become sensitive to touch. By the eighth week her own unique fingerprints start to form, along with the lines in her hands.
A vast majority of abortions are performed during this time, despite the scientific facts which clearly show that an individual human life is developing, as it would after birth, from infant to child to adolescent to adult.
In an important article, Professor John T. Noonan argues that it is reasonable to infer that toward the end of the second month of pregnancy the unborn has the ability to feel pain.  It is crucial to remember that the end of the second month (7 to 8 1/2 weeks) is in the first trimester, a time at which a great majority of abortions are performed and at which the Supreme Court said a state may not prohibit abortions performed by a licensed practitioner. From the facts of brain and nerve development, the pained expressions on the faces of aborted fetuses, the known ability to experience other sensations at this time, and the current methods by which abortions are performed, Noonan concludes from his research that as soon as a pain mechanism is present in the fetus — possibly as early as day 56 — the methods used will cause pain. The pain is more substantial and lasts longer the later the abortion is. It is most severe and lasts the longest when the method is saline poisoning.
Whatever the method used, the unborn are experiencing the greatest of bodily evils, the ending of their lives. They are undergoing the death agony. However inarticulate, however slight their cognitive powers, however rudimentary their sensations, they are sentient creatures undergoing the disintegration of their being and the termination of their vital capabilities. That experience is painful in itself. 
Movement is what characterizes the third month of pregnancy. Although she weighs only one ounce and is comparable in size to a goose egg, the unborn begins to swallow, squint, and swim, grasp with her hands, and move her tongue. She also sucks her thumb. Her organs undergo further development. The salivary glands, taste buds, and stomach digestive glands develop — as evidenced by her swallowing and utilization of the amniotic fluid. She also begins to urinate. Depending on the unborn’s sex, primitive sperm or eggs form. Parental resemblance may already be seen in the unborn’s facial expressions.
Fourth and Fifth Months
Growth is characteristic of the fourth month. The weight of the unborn increases six times — to about one-half her birth weight. Her height is between eight and ten inches long and she can hear her mother’s voice.
In the fifth month of pregnancy the unborn becomes viable. That is, she now has the ability, under our current technological knowledge, to live outside her mother’s womb. Some babies have survived as early as twenty weeks. The fifth month is also the time at which the mother begins to feel the unborn’s movements, although mothers have been known to feel stirrings earlier. This first movement was traditionally called quickening, the time at which some ancient, medieval, and common-law scholars thought the soul entered the body. Not having access to the biological facts we currently possess, they reasoned that prior to quickening it could not be proven that the unborn was “alive.” Current biology, by conclusively demonstrating 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.
During the fifth month, the unborn’s hair, skin, and nails develop. She can dream (rapid eye movement [REM] sleep) and cry (if air is present). It is, however, perfectly legal under Roe v. Wade and Doe v. Bolton to kill this unborn human being by abortion for any reason her mother so chooses.
In the remaining four months of pregnancy the unborn continues to develop. The child’s chances of survival outside the womb increase as she draws closer to her expected birthday. During this time she responds to sounds, her mother’s voice, pain, and the taste of substances placed in the amniotic fluid. Some studies have shown that the child can actually learn before it is born.  The child is born approximately 40 weeks after conception.
In summary, the pro-life advocate believes that full humanness begins at conception for at least four reasons, which were evident in the above presentation of fetal development: (1) At the moment of conception a separate unique human individual, with its own genetic code, comes into existence — needing only food, water, shelter, and oxygen in order to grow and develop. (2) Like the infant, the child, and the adolescent, the conceptus is a being who is in the process of becoming. She is not a becoming who is striving toward being. She is not a potential human life but a human life with great potential. (3) The conceptus is the sexual product of human parents, and whatever is the sexual product of members of a particular mammalian species, is itself a unique individual member of that species. And (4) the same being that begins as a zygote continues to birth and adulthood. There is no decisive break in the continuous development of the human entity from conception until death that would make this entity a different individual before birth. This is why it makes perfect sense for any one of us to say, “When I was conceived…”
DECISIVE MOMENT THEORIES: A CRITIQUE
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.  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.”  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,  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,  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.”  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.”  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.  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. 
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.  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.  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.” 
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. 
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.  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. 
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 Haag  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.” 
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.” 
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.”  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”).
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.”  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.” 
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.”  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.”  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.”  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. 
 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.
 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.
 James J. Diamond, M.D., “Abortion, Animation and Biological Hominization,” Theological Studies 36 (June 1975): 305-42.
 Krason, 341.
 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.
 Ibid., 151-52.
 See Mortimer Rosen, “The Secret Brain: Learning Before Birth,” Harper’s, April 1978, 46-47.
 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).
 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.
 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.
 Bernard Nathanson, M.D., Aborting America (New York: Doubleday, 1979), 213-17.
 Ibid., 216.
 Ibid., 217.
 Ibid., 214.
 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.
 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.
 Geisler, Christian Ethics, 153.
 See Varga, 64-65.
 Ibid., 65.
 Robert Wennberg, Life in the Balance: Exploring the Abortion Controversy (Grand Rapids: William B. Eerdmans Publishing Co., 1985), 71.
 Ernest Van Den Haag, “Is There a Middle Ground?”, National Review, 12 December 1989, 29-31.
 Ibid., 30.
 Davis, 58.
 Ibid., 59.
 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.
 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.
 Wennberg, Life in the Balance, 77.
 Singer and Kuhse, 146.
 Wennberg, 77-78.
Francis J. Beckwith, Christian Research Journal, Spring, 1991, page 8.