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.)

The local five minute hypothesis, the Big Bang and creation

The local five minute hypothesis is that the earth, with everything on it, and the environment five light-minutes out from it, come into existence five minutes ago.

Let’s estimate the probability of getting something like a local five minute hypothesis by placing particles at random in the observable universe. Of course, in a continuous spacetime the probability of getting exactly the arrangement we have is zero or infinitesimal. But we only need to get things right to within a margin of error of a Planck distance for all practical purposes.

The volume of the observable universe is about 10⁸⁰ cubic meters. The Planck volume is about 10⁻¹⁰⁵ cubic meters. So, getting a single particle at random within a Planck volume of where it is has a probability of about 10⁻¹⁸⁵.

But, if we’re doing our back-of-envelope calculation in a non-quantum setting (i.e., with no uncertainty principle), we also need to set the velocity for the particles. Let’s make our margin of error be the equivalent of moving a Planck distance within ten minutes. So our margin of error for velocity in any direction will be about 10⁻³⁵ meters in 600 seconds, or about 10⁻³⁸ meters per second. Speeds range from 0 to the speed of light, or about 10⁸ meters per second, so the probability of getting each of the three components of the velocity right is about 10⁻⁴⁶, and since we have three directions right is something like 10⁻¹³⁸. The probability of getting both the position and velocity of a particle right is then 10^{−(185 + 138)} = 10⁻³²³. Yeah, that’s small. Also, there are about 100 different types of particles, and there are a few other determinables like spin, so let’s multiply that by about 10⁻³ to get 10⁻³²⁶.

The total mass of planetary stuff within around five light minutes of earth—namely, Earth, Mass and Venus—is around 10²⁵ kilograms. There are no more than about 10²⁵ atoms, and hence about 10²⁷ particles, per kilogram. So, we have 10⁵² particles we need to arrange within our volume.

We’re ready to finish the calculation. The probability of arranging these many particles with the right types and within our position and velocity margins of error is:

• (10⁻³²⁶)¹⁰⁵² ≈ 10^{−102.5 × 1052} ≈ 10⁻¹⁰⁵⁵.

Notice, interestingly, that most of the 55 comes from the number of particles we are dealing with. In fact, our calculations show that basically getting 10^N particles in the right configuration has, very roughly, a probability of around 10^{−10N + 3}.

So what? Well, Roger Penrose has estimated the probability of a universe with an initial entropy like ours at 10⁻¹⁰¹²³. So, now we have two hypotheses:

• A universe like ours came into existence with a Big Bang

• The localized five minute hypothesis.

If there is no intelligence behind the universes, and if probabilistic calculations are at all appropriate for things coming into existence ex nihilo, the above probability calculations seem about right, and the localized five minute hypothesis wins by a vast margin: 10⁻¹⁰⁵⁵ to 10⁻¹⁰¹²³ or, roughly, 10¹⁰¹²³ to 1. And if probabilistic calculations are not appropriate, then we cannot compare the hypotheses probabilistically, and lots of scepticism also follows. Hence, if there is no intelligence behind the universe, scepticism about everything more than five minutes ago and more than five light minutes from us follows.

The five minute hypothesis

Let S(t) be the state our universe actually has t units of time after the Big Bang.

Let’s suppose that our universe begins at time 0, i.e., at the Big Bang. Then we can ask this question:

1. Why did the universe begin to exist in state S(0) rather than in one of the infinitely many states S(t) for t > 0?

If naturalism is true, the universe’s beginning as it does is probably a brute (unexplained) contingent fact. And while the state S(0) is rather different in physical arrangement from the states S(t) for t > 0, it does not seem different with respect to the likelihood of brutely coming into existence ex nihilo. So the question (1) is not easily to be dismissed, in the way that one might dismiss the question “Why is the third digit of the gravitational constant in SI units a 7 instead of some other digit?” by saying “Well, it had to something, and there is nothing special about 7.” For there is something special about S(0), namely that it is a singularity state that blocks retrodiction, but this something special does not seem relevant to the likelihood of brutely coming into existence—if only because brute coming into existence cannot be probabilistically quantified.

Theism, on the other hand, provides a satisfying answer to (1). First, as a warmup, we might have a good theistic story why the initial state isn’t S(t) for a very large t: perhaps the universe will no longer be habitable after t, and God has good reason to create a habitable universe. Second, we have a good reason why the initial state should be S(0): a singularity is a natural barrier to retrodiction, and so creating a universe whose past goes back to a singularity is creating a universe where the retrodictive knowledge of beings like us is maximized (cf. Robin Collins’ ideas on our world being optimized for science). And knowledge is good. So God has reason to create a world in initial state S(0).

Technical note: Perhaps there is no singularity state S(0), but instead there are states S(t) for t > 0. If so, then replace S(t) in the above argument by something facts about limits from above of S(t). Abstractly, we can form such units as disjunctions of shrinking conjunctions: let U(t)=⋁_δ>0⋀_0<ϵ<δS(t+ϵ), and say that the universe “begins to exist in state U(t)” provided that it doesn’t exist time t or earlier, but that U(t) correctly describes an opening interval of the universe’s existence. Then replace (1) with the question:

2. Why did the universe begin to exist in state U(0) rather than in one of the infinitely many states S(t) or U(t)?

A defense of the five minute hypothesis (given a certain false assumption)

Plausibly:

1. If the universe came into existence either for no cause at all or randomly, it is a priori more likely that it came into existence in a higher-entropy state rather than a lower-entropy one.
2. If the universe came into existence fully-formed five minutes ago ("five minute hypothesis"), it came into existence in a higher-entropy state than if it came into existence 13.8 billion years ago ("scientific orthodoxy").
3. So, if the universe came into existence either for no cause at all or randomly, the five minute hypothesis would be a priori more likely than scientific orthodoxy.
4. But there is no a posteriori evidence for scientific orthodoxy over the five minute hypothesis.
5. So, if we think the universe came into existence either for no cause at all or randomly, it is not rationally consistent for us to believe scientific orthodoxy over the five minute hypothesis.

I personally think premise (1) is dubious: I doubt there are meaningful probabilities for the universe to come into existence for no cause at all or randomly. But if there are no meaningful probabilities, then it is not a priori more likely that it come into existence as scientific orthodoxy claims, and the rest of the argument should continue to go through.

Of course, I think we should believe scientific orthodoxy over the five minute hypothesis, so we should reject the no-cause and randomness hypotheses in (1).

An amusing rhetorical way to present the argument is that if the universe came into existence for no cause at all or randomly, we shouldn't prefer scientific orthodoxy to certain young earth views.