Wednesday, March 21, 2018

Bohmianism and God

Bohmian mechanics is a rather nice way of side-stepping the measurement problem by having a deterministic dynamics that generates the same experimental predictions as more orthodox interpretations of Quantum Mechanics.

Famously, however, Bohmian mechanics suffers from having to make the quantum equilibrium hypothesis (QEH) that the initial distribution of the particles matches the wavefunction, i.e., that the initial particle density is given by (at least approximately) |ψ|2. In other words, Bohmian mechanics requires the initial conditions to be fine-tuned for the theory to work, and we can then think of Bohmian mechanics as deterministic Bohmian dynamics plus QEH.

Can we give a fine-tuning argument for the existence of God on the basis of the QEH, assuming Bohmian dynamics? I think so. Given the QEH, nature becomes predictable at the quantum level, and God would have good reason to provide such predictability. Thus if God were to opt for Bohmian dynamics, he would be likely to make QEH true. On the other hand, in a naturalistic setting, QEH seems to be no better than an exceedingly lucky coincidence. So, given Bohmian dynamics, QEH does support theism over naturalism.

Theism makes it possible to be an intellectually fulfilled Bohmian. But I don’t know that we have good reason to be Bohmian.


Walter Van den Acker said...


Why would a Bohmian interpretation require more fine-tuning than other interpretations? Isn't the the fine-tuning argument supposed to show that, on naturalism, the existence of the universe is an exceedingly lucky coincidence anyway?

The problem I see with a Bohmian interpretation is that it suggests a fully deterministic account of God's creative act, which, in turn, contradicts libertarian free will.

Alexander R Pruss said...

The Bohmian interpretation requires a precise correlation between the initial values of the wavefunction and the distribution of particle positions, a correlation which the theory does not posit. This is actually a *massive* amount of finetuning.

As for determinism, it could always be that our acts of free will are miracles from the point of view of physics.

Walter Van den Acker said...


It can be argued that on a Bohmian interpretation only one universe is possible, namely ours.
Compare that to the hypothesis that God could only have created one universe, namely ours. The second option is less parsimonious.
So, actually, the Bohmian interpretation supports naturalism over theism.