personhood: not just a matter of biology

(a work in progress; click "read more" to see the whole thing)

Biological unity. Despite earlier doubts, Joe Carter argues that life begins at conception, end of story. Human identity is sewn up by a matter of biology. Carter quotes Robert George, who writes,

Human embryos possess the epigenetic primordia for self-directed growth into adulthood, with their determinateness and identity fully intact. The adult human being that is now you or me is the same human being who, at an earlier stage of his or her life, was an adolescent, and before that a child, an infant, a fetus, and an embryo. Even in the embryonic stage, you and I were undeniably whole, living members of the species homo sapiens. We were then, as we are now, distinct and complete (though in the beginning we were, of course, immature) human organisms; we were not mere parts of other organisms.

But is it really that simple? No.

First, George's tale of the zygote omits an essential component: the mother. Embryonic growth (and consequent fetal development) is not "self-directed," but rather is a complex interplay requiring maternal contributions. (See here and here for just two examples.) An embryo grown in vitro will die after nine days unless implanted. This is what leads Thomist philosopher Jason Eberl to declare that an embryo must implant in order to reach its full potential and become intellectually ensouled.

Second, consider a common human experience: two sperm penetrate and fertilize two ova, spawning two zygotes. At this point, George would have to agree that two human beings have been created, with "determinateness and identity fully intact." But here's where it gets weird. In rare cases, the zygotes fuse, and form a single entity: a tetragametic chimera.

As the organism develops, the resulting chimera can come to possess organs that have different sets of chromosomes. For example, the chimera may have a liver composed of cells with one set of chromosomes and have a kidney composed of cells with a second set of chromosomes. This has occurred in humans, though it is considered extremely rare.

Affected persons are identified by the finding of two populations of red cells or, if the zygotes are of opposite sex, ambiguous genitalia and hermaphroditism alone or in combination; such persons sometimes also have patchy skin, hair, or eye pigmentation (heterochromia). If the blastocysts are of the same sex, it can only be detected through DNA testing, although this is a rare procedure. Thus the phenomenon may be more common than currently believed.

Regardless of its rarity, tegragametic chimerism strikes a fatal blow to the embryo-as-person concept.¹ When heterozygotic twins fuse, George would have to admit that a human being gets lost in the combination, and, mysteriously, 1+1=1.

Robert George's position is a form of reductionist physicalism.

Thus, what each of us refers to as "I" is identically the physical organism that is the subject both of bodily actions, such as perceiving and walking, and of mental activities, such as understanding and choosing. Therefore, you and I are physical organisms, rather than consciousnesses that merely inhabit or are "associated with" physical organisms. And so, plainly, we came to be when the physical organism we are came to be; we once were embryos, then fetuses, then infants, and so on.

This is what surprises me about George's--and, by extension, Carter's--adoption of a solely biological criterion for establishing personhood. Carter, in a piece attacking reductionism, writes,

Whereas the Christian believes that all aspects of reality* (physical, social, biological, spatial, physical, etc.,) are dependent upon God’s sustaining power and can therefore be interdependent, the unregenerate thinker will eventually claim that one aspect is identical with or depends on another.

In the previous post we saw how this worked out in the field of mathematics. Leibnitz related all aspects of reality to the mathematical. Mill reduced not only the mathematical aspect but all pretheoretical experience to the sensory aspect. In a similar manner, Russell folded the mathematical aspect into the aspect of logic while Dewey reduced it to the biological. These examples are typical of the way that presuppositions about the way that aspects of reality relate to one another control the theory-making process.

Examine any theory from the social or natural sciences that were later discredited and you will find a common thread: they all reduce at least one aspect of reality to another and treat one aspect as primary. The problem with this, as philosopher Roy Clouser notes, is that it assigns some part of creation the role of lawgiver to creation. Because the non-theists denies a role for a self-existent creator and sustainer, they must invoke some aspect of creation to perform those essential functions.

Naturally, such attempts to treat an aspect of creation as “divine” will prove futile. But the non-theist has no other choice. Forced to explain one aspect as a reduction of another (i.e., the “mind” reducible solely to the physical brain) they must necessarily embrace either absurdity (e.g., eliminative materialism) or logical incoherence (e.g., how does a physical object “know” another physical object?).

*_{These aspects of reality are more thoroughly explored by the late Christian philosopher Herman Dooyeweerd and his “theory of modal aspects.” Dooyeweerd believed that God created certain laws and norms of reality that were both irreducible yet interrelated. Though the list wasn’t exhaustive, he spelled out 15 “spheres of human life and experience”: Spatial ; Kinematic, Physical (energy + mass), Biotic (life functions), Sensitive (sense, feeling, emotion) ; Analytical (distinction) ; Formative (deliberate shaping: history, culture, technology, goals and creativity) ; Lingual (meaning carried by symbolic) ; Social (social interaction) ; Economic (frugal use of resources) ; Aesthetic (harmony, surprise, fun); Juridical (due) ; Ethical (self-giving love, generosity) ; and Pistic (vision, aspiration, commitment, creed).}

As John Lizza writes about the "biological paradigm of death,"

Only the nonreductionist view of persons "takes people seriously" in an ontologically and morally charged sense.... [A]ny strictly biological definition of death assumes some materially reductionist view about humanity or personhood.... [S]ince any strict biological definition of death assumes some reductionist view, those who reject such views ought to reject the idea that defining death is a strictly biological matter (Preface, xi).

Lizza goes on to explain that the same principles hold for considering life's beginning--and that we should take a "constitutive view" of human persons. Human persons are constituted by, but not coequal to, human bodies.

There are other ways of approaching human identity that attempt to use biology to inform a non-reductionist view of the human person. Jason Eberl's Thomist perspective mentioned above combines Aquinas's view of the three types of souls--vegetative, sensitive, and intellective--with biological reality.Eberl writes,

Once implantation occurs, twinning is no longer possible, and cell differentiation between the embryo proper and extraembryonic material is complete, the instance of matter that is the embryo proper can be said to be an individual instance of matter, informed by one form, viz., the intellective soul.

At the formation of the primitive streak, there is a living biological organism, capable of nutrition and growth, developing the earliest biological tools necessary for sensation, imagination, and rational thought (being that all of these powers are tied to the brain and spinal cord that develop from the primitive streak). Therefore, at this point, the powers proper to the vegetative type of soul are actualized (life,
nutrition, growth) and the powers proper to the sensitive type of soul are informing the biological organism to develop the tools necessary to actualize the powers of sensation and imagination. Also, the powers proper to the intellective type of soul are informing the same development in order to actualize the power of rational thought. The specific powers of sensation and intellection are not themselves actualized until the required organs begin to function. However, the soul itself is active by informing the body to develop the required organs. Therefore, I conclude that the human person is instantiated as an individual complete biological organism with the powers of life, sensation, and rational thought (i.e., a being with both a body and a human intellective soul) at the moment the primitive streak begins to
form, division of the organism (i.e., twinning) is no longer possible, and cells which form the embryo proper are determined to that end and no other.

¹Daniel Gazzaniga attempts to make this point, writing,

Additionally, even divided embryos can recombine back into one. The happy result would be a person who has emerged from two distinct fertilized eggs but is otherwise just like you and me. The "person = zygote" theory would have to say that he is two people!

Though he confuses "divided embryos" and "two distinct fertilized eggs," he's on the right track.