Predictive Minds Can Be Humean Minds

The Predictive Processing (PP) literature contains at least two different versions of the framework with different theoretical resources at their disposal. One version appeals to so-called optimistic priors to explain agents’ motivation to act (call this Optimistic PP). A more recent version appeals to expected free energy minimization to explain how agents can decide between different action policies (call this Preference PP). The difference between the two versions has not been properly appreciated, and they are not sufficiently separated in the literature. They constitute two different theories with strikingly different accounts of motivation and action. By reducing all desire-like constructs to belief-like constructs, Optimistic PP entails a substantial revision of standard accounts of motivation and action in philosophy and cognitive science. By contrast, Preference PP introduces desire-like constructs that play Humean motivational roles in the explanation of action. In this Humean iteration, PP resembles other prominent computational frameworks implementing a distinction between beliefs and desires, such as Reinforcement Learning and Bayesian Decision Theory. Ultimately, PP faces a dilemma between parsimony of mental constructs and completeness of its explanations of agency and the mind.