Is agency prohibited by the PSR?


Bar biked away from the gym and I sat on the low wall outside and had a Buddhistic vision. I saw the principle of sufficient reason (PSR) running everything. Everywhere there were people walking. Apparently intentionally. I felt very relaxed after our workout, so their sharp, intentional movements struck me. Were their movements any different from those of falling leaves, or kicked rocks, or floating dust particles?

What was driving these brisk walkers?

We think of the world as a deterministic machine. Except for humans, which, we like to believe, are driven by ghosts. But then for the sake of consistency, since the parts determine the whole, every atom must be ghost-driven as well. So humans are not ghost-driven after all.

Is the world really a mix of determined physics and free agency? Do atoms become freed of their regulation simply by placing them inside a body? Do atoms in certain configurations somehow augment or amplify the uncertainty that’s already running? Is the brain an indeterminacy amplifier?

We don’t take the PSR seriously enough.

For a moment I saw it, the PSR, running everything. For why should we say, “Yes, it applies here” to a billiard or an embryo, but not here, in my cortex, in the spatial seat of my will?

Even an infant is run by the PSR. Consider a particular infant behavioral sequence: (1) It opens its eyes and then (2) its left foot twitches up and then (3) its head rolls to the right and then (4) its eyes look down. Let’s call this sequence S. What produced sequence S? Besides internal action and external (environmental) action, what else could have produced it? Given its internal state, and given the environment producing upon it certain sensory perturbations, the infant’s behavior could not have been otherwise. The infant does not have “sufficient free agency” to have done otherwise.

But the movements of an adult brain and body, we feel, are different. The adult has an internal state, physically determined; and the internal perturbations produced in it by the environment are also physically determined. But there is still, we insist, leeway for free agency. If this is so, it can only be because the brain somehow amplifies quantum indeterminacy. Otherwise, there could be no free agency.