Criteria of Personhood or Humanity
He starts by looking at the question of what it is to be human or to be a person, citing a few historical references of individual characteristics--being rational, being "in relationship," and "the capacity for self-objectification." He expresses doubt that any single characteristic is appropriate, on the grounds that human beings undergo changes of state such as being asleep or being drugged, or not thinking. I agree with him that the characteristics he has listed won't do the trick, and I also agree with him that features that go away when we sleep are inadequate. But it doesn't follow that there is no single feature that can do the trick--if the feature is a capacity that we have, for example, that capacity doesn't cease to exist when it's not being used.
He goes on to note that lack of personhood doesn't entail that any treatment is morally permissible, pointing out animals as examples of nonpersons that deserve humane treatment. Again, I agree with him--and observe the converse, that possession of personhood doesn't mean that there are no cases where it can be moral to kill a person--cases of self-defense, euthanasia, capital punishment, or war come to mind as possibilities. But what makes animals deserve humane treatment is that they have certain capacities and interests, such as an inner mental life that includes at the very least the ability to feel sensations--and note that humane treatment doesn't necessarily entail a right to life on the part of an animal, or a duty on our part not to kill them.
Vocab appears to want to lay the groundwork for rejecting the use of a criterion of personhood in favor of a criterion of humanity as his standard for arguing against abortion, but here he only offers a promissory note and doesn't provide an argument to that effect. I think this is a mistake, however, because ethical distinctions should be based on morally relevant features, and I don't believe species membership is any more relevant in and of itself to being the holder of rights or of being the object of duties than is race or gender. If a member of an intelligent alien species capable of language were to make contact with us, my intuition is that we would attribute personhood to that entity and give it the same consideration as a human being. Likewise if we manage to build artificially intelligent, self-directed machines with beliefs, desires, and intentions, though the intuition is not as strong there unless I imagine them to have mental lives similar to our own.
Even though Vocab hasn't yet given a reason to reject a personhood criterion in favor of a human being criterion, the rest of his case is solely about human life rather than personhood, which I think is the wrong issue for the reasons I just gave. He argues that human life begins at conception, and clarifies that he means fertilization rather than implantation. This choice means that 30-50% of human lives are spontaneously aborted due to the failure of the fertilized ova to implant in the uterine wall. If Vocab thinks that this loss of human life is the loss of beings with rights and interests to whom we owe a duty to enable them to live out normal lives, then he has some explaining to do. First of all, why would a loving God create a human reproductive system that resulted in such a Holocaust of lives lost before they get a chance to start? Second, why has no one considered this to be a serious ethical problem that we need to urgently devote medical resources to address? We can call this the problem of natural abortion, which has both a natural evil and human evil component that requires justification.
Complete at Fertilization?
Vocab says that at conception (by which he means fertilization), "every human is complete and alive." I agree that a fertilized human ovum is alive--as life is a continuous process, arising from living components, at least until synthetic biology gets to the point of creating life from entirely nonliving components. Sperm and ova are also alive. But it is certainly not complete--zygotes have no brains, no central nervous systems, no organs, no body parts other than undifferentiated, identical cells.
An Individual at Fertilization?
Vocab also says that at fertilization and pre-implantation, "it is not merely a collection of cells lumped together but an actual individual." This also need not be the case. At fertilization, a zygote is an undifferentiated cell that undergoes a process of division without changing size for several days, to become a blastocyst by about the fifth day. During this period each of its cells is totipotent, meaning that each individual cell has the potential to become a full human being. Sometimes more than one of the cells does become a separate human being, as in the case of identical twins. In the case of identical twins, if they don't split completely, they may become conjoined twins or parasitic twins, or one twin may be completely absorbed into the other or otherwise fail to develop and become a vanishing twin. Where a vanishing twin occurs with fraternal twins, the resulting individual can be a chimera, with two sets of DNA. Should we also grieve for those twins who fail to develop, either due to failure to split off or failure to develop?
The science fiction scenarios of teleportation that create interesting philosophical puzzles for the notion of personal identity are real puzzles for a view that attributes personhood to zygotes, though without the additional problem of memories and experiences, since zygotes are undifferentiated cells.
Once the zygote becomes a blastocyst, it forms into an outer layer of cells, which later becomes the placenta, and an inner cell mass of pluripotent embryonic stem cells, each of which is capable of differentiating into any kind of human cell. Only after this stage does the blastocyst implant in the wall of the uterus, about a week after fertilization, and begin taking nutrients directly from the blood of the mother--a dependency that can itself be of moral significance, as Judith Jarvis Thomson's violinist argument shows. As already mentioned above, a great many fertilized ova do not reach this stage. Further, the percentages of implant failure are higher for in vitro fertilization (IVF), a procedure which Vocab's criteria would have to declare unethical, even though it is the only way that many couples can have their own biological offspring.
It should also be noted that the process of therapeutic cloning involves taking a female ovum (which Vocab doesn't seem to indicate he considers to be a bearer of rights on its own), removing its haploid DNA, inserting the nucleus from a (diploid) human somatic cell (this is called somatic cell nuclear transfer), and giving it a shock to cause it to start dividing just like a fertilized egg. This occurs without fertilization by a human sperm. Once it reaches the blastocyst stage, its inner cell mass is harvested for embryonic stem cells, which destroys the blastocyst in the process. The natural process of fertilization never takes place, but there's little doubt that reproductive human cloning is possible via this process. Vocab's choice of fertilization as key suggests that there is no moral issue with this process, even though it also has some potential to become a human being. Further, if fertilization is a necessary, not just a sufficient, condition for rights, Vocab's view suggests that human clones would have no rights.
Vocab goes on to say that "the embryo is already 'fully programmed' (to use computer language). This means the pre-implanted embryo needs no more information input at any further point in its development." While this was formerly believed to be the case about the individual embryo's biology, we now know that the environment of development can play a role in the characteristics that will come to be exhibited, such as from mRNA supplied from the mother to a developing embryo after fertilization and prior to zygote formation. But in any case, I would maintain that it's not our cellular biology that gives us moral value, as opposed to our capacities to have interests, desires, intentions, plans, sensations, and so forth--all capacities that zygotes lack.
Vocab ends this piece with some anthropomorphizing of zygotes, which appears to me to be a highly misleading form of argument--his analogies cannot be taken literally, since zygotes have no mental processes.
Human and Living = Human Being?
I agree with Vocab that a fertilized human ovum is living, that it's human, and that, if all goes well, it will become one (or more) individual human beings. I don't agree that it's yet a person or a "human being," since it lacks the requisite parts and capacities.
To sum up:
- Vocab hasn't given a reason to favor a criterion of "being human" over personhood for determining when it's legitimate to attribute rights or incur duties on our part.
- His choice of fertilization as the point at which rights begin is not when life begins (as it is continuous) and implies that a large percentage of rights-bearing entities die without any apparent concern from God or those who share Vocab's views, an inconsistency requiring justification and explanation.
- A zygote has the potential to be not just one person, but multiple. The same lack of concern over non-actualized multiples that could have been born requires explanation.
- Vocab's view suggests that IVF, which similarly loses even more zygotes or blastocysts (not even counting the embryos that are left frozen or discarded), is unethical.
- Vocab's view so far gives no reason to classify human therapeutic or reproductive cloning as unethical--but might even entail that human clones have no rights, since there's no fertilization by a human sperm, if he thinks that fertilization is both a necessary and sufficient condition for rights.
- In the stages of life described so far, we've gone from completely undifferentiated totipotent cells to a differentiation between two types of cell, the outer wall of the blastocyst (which we both agree is neither a person nor a human being, but what becomes a placenta) and an inner cell mass of embryonic stem cells. Vocab hasn't given a reason why we should give that rights or moral value.
- At this state, the embryo is dependent upon the mother for its existence; Vocab will need to give an account of how the mother's rights are weighed against the embryo's in light of arguments like Judith Jarvis Thomson's violinist example.
- Vocab calls a fertilized zygote a "complete" human being and implies that it has everything it needs to determine its future state, but this is neither the case biologically (given maternal effects on development, for example) nor regarding features that we consider quite important for human value, such as those that develop as a result of acquisition of language, ideas, experiences, and so forth.
- Vocab has used some anthropomorphic language in describing the implantation process which is misleading since zygotes have no mental processes.
UPDATE (December 12, 2009): Added the sentence on chimeras.
UPDATE (December 13, 2009): Vocab has posted a brief rebuttal to this post.