Two decreases in tension between faith and science

Over the past two hundred years or so, one new tension point arose for the relationship between Christianity and science due to scientific progress—namely, evolution. At the same time, several tension points disappeared due two other instances of scientific progress.

The first instance of this scientific progress was the general abandonment of the Aristotelian eternal world model of the universe with Big Bang cosmology. In the middle ages, Jewish, Islamic and Christian thinkers struggled with the tension between the science/philosophy of the day strongly tending towards a universe that always existed and the theological commitment to a creation a finite amount of time ago. That problem is gone.

The second instance is our scientific understanding of the continuity of organic development from zygote to embryo to infant to adult, which has made quite implausible the old view of discontinuous transition in utero from vegetable to animal to human. This old view was the dominant scientific view of human origins until fairly recently, and it had serious tensions with Christian theology.

The first of these embryological tensions was with Christian moral views about abortion. While traditionally Christians opposed both contraception and abortion, abortion was morally seen as a form of homicide. But on the discontinuous transition view, abortion prior to human ensoulment would only be contraception.

The second embryological tension was a technical problem in Christology. Suppose that in the Incarnation we have the vegetable, mere animal and rational animal sequence. Then Aquinas observes there are two possibilities, neither of which is theologically appealing.

First, it could be that God becomes incarnate as a vegetable or a mere animal. But this seems, as Aquinas says, “unbecoming”. And he seem to be right. The Incarnation reveals to us the person of the Logos, and it would be unbecoming that the Logos become a non-personal being.

Second, it could be that the Incarnation happens only at the beginning of the third stage of development, namely once everything is ready for a rational animal. But then Aquinas says “the whole conception could not be attributed to the Son of God”. Indeed, don’t we even have a tension with the Apostles’ Creed line that Christ “was conceived by the Holy Spirit”? For on this option, Christ was not conceived at all. What was conceived was a vegetable, not Christ. (Indeed, none of us were conceived on this view.) Moreover, one might worry that then there would be a sense in which the flesh of Christ would pre-exist the Incarnation. And that makes it difficult to say that the Word became flesh—for the flesh that Scripture says he “became” would already in a sense have been there, and one can’t become this flesh, since this flesh already has its own identity. (Granted, there may well be some Aristotelian metaphysics one can do to lessen this last worry.)

Aquinas solves the problem by supposing that Christ is conceived fully formed in Mary’s womb, and hence has the rational soul from the first moment of his existence. But this solution is itself problematic. Absent gradual development from a zygote, is this conception at all? If God were to create an adult human either ex nihilo or out of some pre-existing matter, we would not consider that a conception. But neither should we then consider it a conception if God creates a fully-formed fetus, even if he does that out of the pre-existing matter of Mary. So we still have a problem with the Apostles’ creed’s “was conceived by the Holy Spirit”. Moreover, it seems that this deprives Mary of a significant chunk of her motherhood.

But the problem entirely disappears once we think that the human beings begin their existence at conception. Christ is conceived by the Holy Spirit, presumably in that Mary’s ovum is transformed into a zygote by the infinite power of the Holy Spirit, which zygote is the Christ who then grows in utero like we all do.

(Catholics also note that the new scientific understanding of human embryonic development also helps with the doctrine of Mary’s immaculate conception—for only a rational being can be immaculately conceived, since original sin or freedom from it can only apply to a rational being.)

Aquinas's embryology and the theory of relativity

Aquinas famously thinks that there is a succession of forms in utero, with first a vegetable form, then an animal form, and then a rational animal (human) form. No two of these forms are had simultaneously.

But if a three-dimensionally extended object that has form A comes to be a three-dimensionally extended object that has form B, with no other forms intervening, then, in every inertial reference frame except for at most one, there is a time at which some of the matter has form A and some of the matter has form B. So unless there is a privileged frame, Aquinas’s story doesn’t work.

In the following diagram, the slanted dashed line indicates a reference frame where some of the matter has form A (red) and some has B (blue).

Here is a variant that could work, but does not seem very plausible. We could imagine that when we have a transition from A to B, the matter of A, except at one point, passes to B through one or more other forms, indicated by the yellow portion of the diagram. These might be forms of mere particles, or they could be some special forms. In other words, A dies off into a point, with the dead matter acquiring transitional forms, and then B starts growing from the last point of A, incorporating the transitional forms. Where the A and B substances meet will be a point either of A or of B, but not of both. The narrowing of A and the growth of B happen at the speed or light or less.

On this variant, no inertial frame contains both A and B points. (If light moves at 45 degrees from horizontal in the diagram, then inertial frames correspond to lines like the dashed one making a less than 45 degree angle with the horizontal.)

But there is something rather weird going on here. Suppose that A is the vegetable form and B is the animal form (a similar argument will apply if A is the animal form and B the human form). Then close to the pointy meeting between A and B, the yellow stuff contains the vast majority of what biology would call “the embryo”, and a fairly well-developed one, since it’s on the cusp of becoming an animal. Yet the vast majority of that “embryo” is the yellow stuff—neither the vegetable nor the animal, but something else, maybe mere atoms. Indeed, once we get close enough to the meeting point, the yellow will materially function just like an embryo, since a tiny subatomic hole makes no difference to material functioning. This is very odd, and gives us reason to reject Aquinas’s story.

Of course, the main alternative to Aquinas’s story is that the gametes change into a human being. That faces some of the same difficulties. However, I think the difficulties are less if the gametes are not themselves a substance, but a plurality of substances, perhaps particle-substances. In the diagram below, the gamete-stuff is in yellow, and the blue indicates the human being. We still have the problem that early on most of what we have will need to be biologically very close to a functioning zygote, and yet it is in yellow, except for a small blue hole corresponding to where ensoulment is spreading out from a single point. But I think this is less problematic, because at this juncture the yellow stuff is something that is less obviously an organism. (Admittedly, the blue stuff is less obviously an organism when it is nearly a point. But what makes it an organism is that while its matter has little going for it, it’s got the right form.)

So, relativity makes it hard to hold on to Aquinas’s embryology. Which is a nice thing for pro-life Thomists who want to defend ensoulment at conception and hence deny Aquinas's embryology--or Catholic Thomists who find the doctrine of the Immaculate Conception incompatible with that embryology.

Maybe there is some way of getting out of this by using the considerations from yesterday’s post, though.