The Type III Dimension Postulate · Rev 3 and the Complete Structure-Side Chapter (2026b through 2026o, with Closing Statement and Position Statement)

This deposit gathers the complete structure-side chapter of the Reid Postulate following its acceptance by the International Journal of Quantum Foundations / Quantum Speculations on 2 May 2026. The framework proposes that the dimensions of physical description are not all the same structural kind. It names the unargued assumption that they are, the Homogeneity Postulate, and lifts it, proposing categorical separation between Type I (spatial), Type II (entropic), and Type III (observational) dimensions. Observation is articulated as a Type III index on a fiber bundle over four-dimensional spacetime, with binary fiber Ω carrying purely indexical distinction between two members of identical Lorentzian content. The Born-compatible measure inherits from Gleason's theorem on the projection lattice. Composability requires jointly describable systems to share index. A companion no-go theorem closes one class of candidate dynamics, articulating a combined kinematic and dynamic no-go boundary. The reader will encounter the framework's articulation in three layers. The Postulate body (Rev 3) and the no-go theorem (2026b) carry the framework's standing content. The synthesis layer (2026c through 2026i) articulates that content at distinct registers, including minimal structure, the structure to fact fence, Gleason compatibility, scope conditionality, algebraic conditions, Hilbert space level conditionality, and the contextuality stack, without extending the framework's claims. The post closure arc (2026j through 2026o) is the chapter's actual completion: the section articulation extension (2026j Rev 4), the synthesis register filing on joint describability failure as structural principle (2026k), the prediction note articulating the framework's structural prediction in Bell type scenarios at the level of object ontology (2026l), and the construction trilogy specifying the algebra to section map (2026m), verifying it on safe regimes (2026n), and exploring whether the framework produces quantitative content of its own (2026o, which finds the framework's reach to be qualitative structural rather than quantitative numerical). The Closing Statement (15 May 2026) marked the chapter procedurally complete. The Position Statement articulates the chapter's substantive final standing after the post closure arc produced what the chapter's articulated content required. The framework stands as a structural account of the indexical dimension of physical description, internally consistent on safe regimes, with load bearing commitments named honestly, falsification conditions stated, and open problems located and not resolved. The framework does not derive standard quantum mechanics but is consistent with it. It does not resolve the measurement problem. It does not produce new empirical predictions beyond the object ontology level. What the framework does not claim is part of what it offers. The work is offered for technical scrutiny. It adds no particles, forces, symmetries, or universes. It operates by removing an assumption rather than adding structure. Submitted for technical scrutiny, not belief.