I thought the following was very interesting:

Soft pro-choicers give reasons for thinking there are. Their position can be fairly summarized, I think, in seven arguments. Each attacks a basic pro-life syllogism by accusing it in different ways of using an ambiguous middle term, “human being.” They say a fetus is a human life but not a human person:

First , there is the linguistic fact that we can and often do make a triple distinction among a human life, a human being and a human person. Each cell in our bodies has human life, and a single cell kept alive in a laboratory could be called “a human life” but certainly not “a human being” or “a human person.” “A human being” is a biologically whole individual of the species. Even a human being born with no brain is a human being, not an ape; but it is not a person because it has no brain and cannot do anything distinctively human: think, know, choose, love, feel, desire, commit, relate, aspire, know itself, know God, know its past, know its future, know its environment, or communicate — all of which have, in various combinations, been offered as the marks of a person. The pro-life position seems to confuse the sanctity of the person with the sanctity of life, which is two steps removed from it.

Thus pro-life seems to be based on a linguistic confusion. Not all human life is sacred. Not even all human beings, individual members of the human species, are sacred. But all human persons are sacred.

Second, pro-lifers seem to commit the intellectual sin of biologism, idolatry of biology, by defining persons in a merely biological, genetic, material way. Membership in a biological species is not morally relevant, not what makes persons sacred and murder wrong. Membership in the human species is no more morally relevant than membership in the subspecies, or race. If racism is wrong, so is speciesism.

Third , the very young product of conception, the zygote, has no ability to perform any of the distinctive activities that anyone associates with personhood (reasoning, choosing, loving, communicating, etc.) — not even feeling pain, for the zygote has no brain or nervous system. At first it is only a single cell. How could anyone call a single cell a person?

Fourth , it seems to be an obvious mistake for the pro-lifer to claim that personhood begins abruptly, at conception, for personhood develops gradually, as a matter of degree. Every one of the characteristics we use to identify personhood arises and grows gradually rather than suddenly. Pro-lifers seem to be victims of simplistic, black-or-white thinking, but reality is full of greys.

Fifth , pro-lifers seem to confuse potential persons with actual persons. The fetus is potentially a person, but it must grow into an actual person.

Sixth , personhood is not a clear concept. There is not universal agreement on it. Different philosophers, scientists, religionists, moralists, mothers, and observers define it differently. It is a matter of opinion where the dividing line between persons and non-persons should be located. But what is a matter of opinion should not be decided or enforced by law. Law should express social consensus, and there is no consensus in our society about personhood’s beginning or, consequently, about abortion. One opinion should not be forced on all. Pro-choice is not pro-abortion but, precisely, pro-choice.

Seventh , a fetus cannot be a person because it is part of another person, the mother. Persons are wholes, not parts. Persons are not parts of other persons, but the fetus is part of another person; therefore, the fetus is not a person.

The first argument — that some human beings are not persons — is to say that only achievers, only successful functioners, only sufficiently intelligent performers, qualify as persons and have a right to life. And who is to say what “sufficient” is? The line can be drawn at will-the will of the stronger. Nature, reason, and justice are then replaced by artifice, prejudice, and power. When it is in the self-interest of certain people to kill certain other people, whether fetuses, or the dying, or enemies of the state, or Jews, or Armenians, or Cambodians, or heretics, or prophets, the killers will simply define their victims as non-persons by pointing out that they do not meet certain criteria. Who determines the criteria? Those in power, of course. Whenever personhood is defined functionally, the dividing line between persons and non-persons will be based on a decision by those in power, a decision of will. Such a decision, given the fallenness of human nature, will inevitably be based on self-interest. Where there is an interest in killing persons, they will be defined as non-persons.

To the second argument, it must be said that “human being” is not a merely biological term because the reality it designates is not a merely biological reality, though it is a biological reality. To identify human beings and persons is not biologism; in fact, it is just the opposite: it is the implicit claim that persons, i.e., human beings, have a human biological body and a human spiritual soul; that human souls inhabit human bodies.

If robots could do all that persons can do behaviorally, they would still not be persons. Mere machines cannot be persons. They may function as persons, but they do not understand that they do not have freedom, or free will to choose what they do. They obey their programming without free choice. They are artifacts, and artifacts are not persons. Persons are natural, not artificial. They develop from within (like fetuses!); artifacts are made from without.

The connection between the two errors of (1) reducing persons to functions and (2) reducing “human being” to a merely biological category is obvious: the first is the root cause of the second. Once a person is defined in terms of functioning, then zygotes, fetuses and even normal newborns are no longer fully persons. What are they, then? Only members of a biological species, “human being.”

This justifies abortion, of course-and infanticide. The camel is a one-piece camel. I know of no argument justifying abortion that does not also justify infanticide.

To the third argument: the zygote has no brain, true, but it does have what will grow into a brain, just as an infant does not have speech but has what will grow into speech. Within the zygote is an already fully programmed individuality, from sex and aging to eye color and aversion to spinach. The personhood of the person is already there, like the tuliphood of the tulip bulb. One must actually be a human being, after all, to grow a human brain.

The fourth argument is right, of course, to say that development is gradual-after conception. Conception is the break, the clear dividing line, and the only one. I am the same being from conception on. Otherwise we would not speak of the growth and development and unfolding of that being, of me. I was once an infant. I was born. I was once in my mother’s womb. My functioning develops only gradually, but my me has a sudden beginning. Once again, the pro-choice objection confuses being a person with functioning as a person.

Furthermore, if personhood is only a developing, gradual thing, then we are never fully persons, because we continue to grow, at least intellectually and emotionally and spiritually. Albert Schweitzer said, at 70, “I still don’t know what I want to do when I grow up.” But if we are only partial persons, then murder is only partially wrong, and it is less wrong to kill younger, lesser persons than older ones. If it is more permissible to kill a fetus than to kill an infant because the fetus is less of a person, then it is for exactly the same reason more permissible to kill a seven-year-old, who has not yet developed his reproductive system or many of his educational and communications skills, than to kill a 27-year-old. The absurd conclusion follows from defining a person functionally.

No other line than conception can be drawn between pre-personhood and personhood. Birth and viability are the two most frequently suggested. But birth is only a change of place and relationship to the mother and to the surrounding world (air and food); how could these things create personhood? As for viability, it varies with accidental and external factors like available technology (incubators). What I am in the womb-a person or a non-person cannot be determined by what machines exist outside the womb! But viability is determined by such things. Therefore personhood cannot be determined by viability.

fifth if the fetus is only a potential person, it must be an actual something in order to be a potential person. What is it? An ape?

There are no “potential persons” any more than there are potential apes. All persons are actual, as all apes are actual. Actual apes are potential swimmers, and actual persons are potential philosophers. The being is actual, the functioning is potential. The objection confuses “a potential person” with “a potentially functioning person”-Functionalism again.

Sixth , is personhood an unclear concept? If it were a matter of degree, determined by degree of functioning, then it would indeed be unclear, and a matter of opinion, who is a person and who is not. Refuting objection four undercuts objection six.

Personhood is indeed unclear-for Functionalism. Such questions as the following are not clearly answerable: Which features count as proof of personhood? Why? How do we decide? Who decides? What gives them that right? And how much of each feature is necessary for personhood? And who decides that, and why? Also, all the performance-qualifications adduced for personhood are difficult to measure objectively and with certainty. To use the unclear, not universally accepted, hard-to-measure functionalist concept of personhood to decide the sharply controversial issue of who is a person and who may be killed is to try to clarify the obscure by the more obscure, obscuram per obscurius.

Seventh , if the fetus is only a part of the mother, a hilariously absurd consequence follows. The relation of part to whole is what logicians call a transitive relation: If A is part of B and B is part of C, then A must be part of C. If a wall is part of a room and the room is part of a building, then the wall must be part of that building. If a toe is part of a foot and a foot is part of a body, then the toe is part of the body. Now if the fetus is a part of the mother, then the parts of the fetus must be parts of the mother. But in that case, every pregnant woman has four eyes and four feet, and half of all pregnant women have penises! Clearly, the absurd conclusion came from the false premise that the fetus is only part of the mother.

I have refuted the pro-choice position (1) in general, by the basic pro-life syllogism, (2) foundationally, by identifying and refuting Functionalism as the root pro-choice error, and (3) specifically, by refuting each of the seven pro-choice arguments against fetal personhood. But just suppose all of my arguments are somehow inconclusive. Suppose I was wrong in my very first point, that abortion is a clear evil. Suppose abortion is a difficult, obscure, uncertain issue. Even if you take this “softest pro-choice” position, which we can call “abortion agnosticism,” you stand refuted by the following quadrilemma.

Either the fetus is a person, or not; and either we know what it is, or not. Thus there are four and only four possibilities:

that it is not a person and we know that, that it is a person and we know that, that it is a person but we do not know that, and that it is not a person and we do not know that.

Now what is abortion in each of these four cases?

In case (1), abortion is perfectly permissible. We do no wrong if we kill what is not a person and we know it is not a person-e.g., if we fry a fish. But no one has ever proved with certainty that a fetus is not a person. If there exists anywhere such a proof, please show it to me and I shall convert to pro-choice on the spot if I cannot refute it. If we do not have case (1) we have either (2) or (3) or (4). What is abortion in each of these cases? It is either murder, or manslaughter, or criminal negligence.

In case (2), where the fetus is a person and we know that, abortion is murder. For killing an innocent person knowing it is an innocent person is murder.

In case (3), abortion is manslaughter, for it is killing an innocent person not knowing and intending the full, deliberate extent of murder. It is like driving over a man-shaped overcoat in the street, which may be a drunk or may only be an old coat. It is like shooting at a sudden movement in a bush which may be your hunting companion or may be only a pheasant. It is like fumigating an apartment building with a highly toxic chemical not knowing whether everyone is safely evacuated. If the victim is a person, you have committed manslaughter. And if not?

Even in case (4), even if abortion kills what is not in fact a person, but the killer does not know for sure that it is not a person, we have criminal negligence, as in the above three cases if there happened to be no one in the coat, the bush, or the building, but the driver, the hunter, or the fumigator did not know that, and nevertheless drove, shot or fumigated. Such negligence is instinctively and universally condemned by all reasonable individuals and societies as personally immoral and socially criminal; and cases (2) and (3), murder and manslaughter, are of course condemned even more strongly. We do not argue politely over whether such behavior is right or wrong. We wholeheartedly condemn it, even when we do not know whether there is a person there, because the killer did not know that a person was not there. Why do we not do the same with abortion?