Catherine Reason’s no-supervenience theorem argues that a physicalist theory cannot consistently account for a self-aware system that establishes with certainty its own conscious condition. This Perspective reconstructs the argument as a conditional no-go result and examines its implications for theories of consciousness and multiscale neuroscience. The central distinction is between an intrinsic conscious function and a system’s metacognitive certification that this function is present and reliably known. Physical supervenience constrains the relationship between physical states and the properties they determine; it does not, by itself, guarantee infallible internal access to those states or their conscious significance. A simple countermodel therefore demonstrates that physical supervenience can be maintained while self-certification remains fallible. Reason’s diagonal argument nevertheless identifies an important limitation: its secure conclusion applies to a class of theoretical models that adopt substantive premises concerning objectivity, modal reasoning, and self-certainty. It does not, independently of those premises, establish the existence of nonstandard physical consciousness or refute physical structure–function dependence as such. As a constructive alternative, this Perspective proposes a relational, heterarchical structure–function formulation for multiscale neuroscience. Neural organization, intrinsic function, metacognitive judgement, and conscious report are treated as distinguishable but empirically related objects of investigation across explicitly defined observational resolutions. The formulation neither claims to resolve the explanatory gap nor assumes that conscious reports constitute consciousness itself. Instead, it establishes a falsifiable framework for investigating resting-state activity, stimulus-evoked responses, and perturbational neurophysiology, with event definitions, cross-resolution mappings, dependencies, uncertainties, and potential adverse findings specified in advance. Reason’s theorem is thus retained as a constraint on claims of infallible self-verification, rather than elevated into an unconditional refutation of physical structure–function dependence.