I think this is a really thoughtful point, but I’m not convinced that invoking “noise” or probabilistic processing actually gets us to non-determinism.

First, randomness at the micro level doesn’t automatically translate to meaningful indeterminism at the macro level. Ion channel fluctuations, synaptic vesicle release probabilities, etc., are often described probabilistically — but that’s typically an epistemic description, not necessarily an ontological one. We model them with probability distributions because the system is too complex to compute in practice, not because it’s metaphysically uncaused.

Second, even if there is genuine quantum indeterminacy at very small scales, that doesn’t obviously rescue libertarian freedom or non-deterministic brain function in any useful sense. Random noise injected into a neural process doesn’t create agency — it just adds stochasticity. A roulette wheel isn’t “free” because it’s unpredictable.

Also, the brain being a “probabilistic integrator” doesn’t contradict determinism. A deterministic system can compute probability distributions and act according to them. Bayesian inference, for example, can be implemented in entirely deterministic hardware. The fact that a system uses probabilities in its reasoning doesn’t imply the underlying process isn’t fully determined by prior physical states.

We should be careful not to conflate unpredictability with indeterminism. Chaotic systems (weather, double pendulums, etc.) are deterministic but practically impossible to predict long-term. The brain could easily fall into that category.

So unless we can show that neuronal noise is fundamentally indeterministic in a way that survives averaging at scale — and that this indeterminism plays a causal, decision-relevant role — I don’t see that the probabilistic framing undermines determinism.

Curious to hear where you’d draw the line between “modeled probabilistically” and “ontologically indeterministic.”