12 thoughts on “But what about tetragametic chimerism?”

  1. OR:
    I must say, the example of chimerism presents a challenge to my view that zygots are truly people! I will have to spend some time thinking about that. But it is also the case that you are going to hell.” :)

    A few thoughts:
    To begin with, my view is committed to the claim that life begins at conception so the zygote is a person. Now I would not identify the genetic code with the person, because I am not a materialist. The principle of identity (the unifying and organizing principle) is something other than the matter. Let’s call it the “soul”. Of course, the unique genetic code is evidence that there is a new individual (John Paul II appeals to this scientific evidence in this argument in Evangelium Vitae).

    So what do we have here? Here is a stab at it:
    When there are two zygotes, you have two persons, two souls, and two unique genetic codes.
    When the two zygotes fuse together, you are left with 1 individual (I don’t think anyone would argue that there are two individuals). So you have 1 individual and so only 1 soul (the soul is the organizing principle and principle of unity). But you have 2 genetic codes. This is freaky, and it makes that individual abnormal. What happened to the other individual (the other ensouled piece of matter)? Well, can’t we say that it was destroyed? That is, only 1 person survived the fusion event.

    This seems possible. Couldn’t you splice/fuse another man’s DNA into my sequence and not change my individuality and even personhood? Since I would still be one thing, not two, no one would say that I was “part him”, would they? But doing so would not mean that the man that carried that DNA was not a real man and it would not entail that I am a not real man.

    Just a shot at it. I would think that some Catholic theologian or philosopher has written on this, though I have not seen it. I’ll try to look it up if I have time.


  2. Short answer – I don’t know. And it might be near impossible to discern, since the soul is not itself an object of empirical study. I’ll fall on that sword since I still think the conception view looks best, all other views about when personhood begins are either arbitrary or morally atrocious.

    Do we agree on this? — there were two individuals (we don’t have to call them “persons”), now there is one.

    I wonder if looking at twinning will help at all. In the case of twinning a single embryo divides and you then have two identical twins. It is analogous to cloning (the asexual creation of a new individual from an individual). In such a case, can we say which was the original? That is, can we say that embryo A is the original one and embryo B is the “natural clone”? (Makes me think of that cartoon video you had posted a while ago). Even if we can’t, I think we’d all still say that there was once only one individual but now there are two. The chimerism just runs in the opposite direction (and you have involuntary destruction instead of involuntary creation)


  3. Dr. Kleiner,

    Can you elaborate on why the moment of conception is probably the moment when the soul enters the body and not some later stage of development, like when the first neuron fires?


  4. I don’t know if the “soul entering the body” is the right way of framing it. I am not (nor are Aquinas and Aristotle) a dualist – I don’t think the soul is one thing over here and the body is some other thing over there. Rather, individuals are soul-body composites (hylomorphic entities), and the soul is the form of the body.

    At conception a new individual is created. We know this because (unlike the egg or sperm taken by themselves), the zygote has its own unique genetic identity and its own unique and “internally driven” course of development. Each individual is hylomorphic. The instant a new individual is made, a new hylomorphic entity has entered the scene.

    By the time a neuron fires, the individual has been around for some time. And here is my point about arbitrariness: If we say “it is once the brain is active” why not say it is not until the brain is fully developed? Why not say it is not until the brain is fully educated? etc etc etc.

    I affirm what JPII writes in Evangelium Vitae:
    “From the time that the ovum is fertilized, life is begun which is neither that of the father nor the mother; it is rather the life of a new human being with his own growth. It would never be made human if it were not human already. This has always been clear, and modern genetic science offers clear confirmation. … Right from fertilization the adventure of a human life begins, and each of its capacities requires time – a rather lengthy time – to find its place and to be in a position to act.”


  5. Hence my skepticism. Since there’s no good place to put a dividing line, why think there is one? I don’t see any necessary connection between “individual is formed” and “unique genetic identity is formed.” I’d say “individual” is an overall useful general term, like “economy” and “surrealism,” but isn’t tied to any real quality.


  6. Are you not an individual, Huenemann? There might be difference in the midst of your identity (a hailstorm of different desires and pulls), but aren’t you “this man” and not “that man”?
    I think the pomo/Nz deconstruction of notions of identity simply goes too far. It strains philosophical reflection to the point of absurdity, to a point where the philosophical reflection no longer speaks to our experience of ourselves.

    Huenemann, friend. Put down the Nz. Come back to reality. :)


  7. Here is an interesting article on abortion and its politics. It is written by a pro-choicer, but offers a very intimate look into the emotional difficulties of abortion decisions.

    The most telling line is where an abortionist admits that the pro-life view more closely aligns with our experience (emotional and otherwise) of sex, conception, and the killing of the unborn. The trouble, for the pro-choicer, is that reality does not fit his values! To my mind, this is the real story with abortion – we have dislocated moral judgments from reality (nothing is less popular than the natural law).

    Read the whole article (it is quite long but very moving) here:

    This is a different problem than the one Huenemann raised – Huenemann asks a much more basic metaphysical question – something like ‘Are unity and being really convertible terms?’ or ‘Is there such a thing as unity/identity, or is this just a philosophical fiction?’ Nz, and the pomo tradition that inherits him, ask a very difficult question here. I think they are right and wrong — right that we have not adequately appreciated difference and have had something of an identity/unity fetish in philosophy. But wrong in thinking that there is no such thing as identity.


  8. I am an individual. I also am tall and of German descent. But I don’t think there are sharp boundaries deciding exactly what makes anyone any of these things. There are plenty of borderline cases, with no real fact to decide if one is in or out of the group in question.


  9. So you do affirm that you are an individual, you are ‘this man’ and not ‘that man’. Though you say there are no “sharp boundaries” for determining such things, you still affirm your own individuality/unity. On what basis? Are you a “borderline case”? Why or why not?

    Do you take “I am an individual” and “I am tall” to be roughly equivalent kinds of judgments? In other words, do you simply reject the substance – accident distinction?

    Last question for Huenemann: You said “Since there’s no good place to put a dividing line, why think there is one?”
    Let’s presume that I grant (don’t hold your breath) that there is no good place to put a dividing line because there is [really] no such thing as an “individual”. As a matter of public policy, don’t we have to draw a line? Doesn’t law and policy pretty well require that we think of people as “individuals”, weighing their rights, interests, etc? Presuming that is true, where should we draw the legally necessary line?


  10. I was not expressing a Magisterial view there (in fact Evangelium Vitae goes out of its way to say that the Church is not expressly committing itself to either the metaphysical or scientific views). But I was expressing what I understand to be the Thomistic position. I think the Thomistic position is quite close to the Jewish view that you express sympathy for. In fact, I think I’d affirm most everything you said in that paragraph there. It makes for an interesting “philosophical argument” for bodily resurrection – we can’t be human and can’t do anything without bodies!
    Aquinas avoids what moderns call the mind-body problem. Aquinas does not think he has this problem because the soul is simply the “power of the body”. See Summa Q75.1, reply to objection 3.

    Yes, it is attractive to have as clear of a view as we can on conception. I think we should work toward that because there is a lot at stake in the abortion argument. But you are quite right that the matter is too mysterious to admit of a tidy reduction. Even John Paul II backs off his argument in Evangelium. Not that he doesn’t think it is a good argument, but he backs away to a posture that more thoroughly appreciates the mystery of what is going on in procreation.

    “Even if the presence of a spiritual soul cannot be ascertained by empirical data, the results themselves of scientific research on the human embryo provide a valuable indication for discerning by the use of reason a personal presence at the moment of the first appearance of human life.”

    Having backed off from the more dogmatic claims (now couching them in terms of “valuable indicators”), he then makes a “best bet” type argument — “the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo.” After all, the possibility of their being innocent life inside a building would warrant an immediate halt to plans to destroy the building (no matter how good our reasons were for wanting to take the building down).


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