<p>Predictive processing is an ambitious neurocomputational framework, offering an unified explanation of all cognitive processes in terms of a single computational operation, namely prediction error minimization. Whilst this ambitious unificatory claim has been thoroughly analyzed, less attention has been paid to what predictive processing entails for structure–function mappings in cognitive neuroscience. We argue that, taken at face value, predictive processing entails an all-to-one structure–function mapping, wherein each individual neural structure is assigned the same function, namely minimizing prediction error. Such a structure–function mapping, we show, is highly problematic. For, barring few, rare occasions, such a structure–function mapping fails to play the predictive, explanatory and heuristic roles structure–function mappings are expected to play in cognitive neuroscience. Worse still, it offers a picture of the brain that we know is wrong. For, it depicts the brain as an equipotential organ; an organ wherein structural differences do not correspond to any appreciable functional difference, and wherein each component can substitute for any other component without causing any loss or degradation of functionality. Somewhat ironically, the very neuroscientific roots of predictive processing motivate a form of skepticism concerning the framework’s most ambitious unificatory claims. Do these problems force us to abandon predictive processing? Not necessarily. For, once the assumption that all cognition can be accounted for exclusively in terms of prediction error minimization is relaxed, the problems we diagnosed lose their bite.</p>