Bayesian Descriptions are not Mechanisms: Predictive Processing and the Realisation Gap in Embodied Neural Dynamics
Predictive processing casts perception, action, and learning as probabilistic inference. This paper asks when a Bayesian description identifies a mechanism. I distinguish computational description, algorithm, and physical implementation. Mechanism requires a causal mapping from physical transitions to inferential roles; behavioural fit cannot establish it. Priors range over model-supplied alternat