Most scholars concerned with the foundations of quantum mechanics (QM) think that contextuality and nonlocality (hence nonobjectivity of physical properties) are unavoidable features of QM which follow from the mathematical apparatus of QM. Moreover these features are usually considered as basic in quantum information processing. Nevertheless they raise still unsolved problems, as the objectification problem in the quantum theory of measurement. The extended semantic realism (ESR) model offers a possible way out from these difficulties by embedding the mathematical formalism of QM into a broader mathematical formalism and reinterpreting quantum probabilities as conditional on detection rather than absolute. The embedding allows to recover the formal apparatus of QM within the ESR model, and the reinterpretation of QM allows to construct a noncontextual hidden variables theory which justifies the assumptions introduced in the ESR model and proves its objectivity. According to the ESR model both linear and nonlinear time evolution occur, depending on the physical environment, as in QM. In addition, the ESR model, though objective, implies modified Bell's inequalities that do not conflict with QM, supplies different mathematical representations of proper and improper mixtures, provides a general framework in which the local interpretations of the GHZ experiment obtained by other authors are recovered and explained, and supports an interpretation of quantum logic which avoids the introduction of the problematic notion of quantum truth.
Von Neumann's Hilbert-space formalism of quantum mechanics constitutes a logico-physical theory of observed or measured reality. Imposing the logical constraint of Booleanity, essential for objectively shareable descriptions among observers, reveals the physical meaning of classicality inherently embedded within the formalism itself. Starting from this consideration, the present work reformulates the quantum-classical transition via Hilbert-space classical mechanics (HCM), grounding classicality not in the dynamical limit (
ℏ→0), but in the logical constraint of Booleanity (i.e., the mutual commutativity of preparable states). Within this state-centric framework, applying the Einstein-Podolsky-Rosen (EPR) criterion alongside locality and measurement independence reduces standard quantum mechanics to the HCM model. Thus, the EPR argument reveals not quantum incompleteness, but the implicit classical boundaries of its own premises. To resolve this impasse, we articulate a nuanced quantum ontology grounded in a fundamental structural bipartition between the observational environment and the observed object, which accommodates three categorical distinctions: ontic, processional, and tropos-existential. Building on this, we propose a criterion of objective reality wherein descriptive objectivity is treated as merely a sufficient condition for physical reality. This addresses the historical Bohr-Einstein ambiguity, enabling the quantum formalism to ontologically unify objective measured phenomena and non-objective observed interference within a context-dependent framework.
Semantic Gravitation is an open research programme that investigates whether meaning can be treated as a dynamical object with its own geometry, stability structure, and flow laws. This third paper develops the quantum-compatible layer of the programme. It shows how the standard formalism of quantum mechanics—quantum states, observables, expectation values, and dynamics—can be embedded faithfully and without modification into the semantic Hilbert-space framework introduced in Papers I and II. Quantum states, represented as density operators on a quantum Hilbert space H_Q, are embedded as a distinguished sector of the global semantic state space S via an explicit linear isometric construction. Expectation values are reproduced exactly by representing quantum observables as continuous linear functionals on the embedded sector, and both unitary and open-system quantum dynamics (including GKLS evolutions) are shown to induce compatible dynamics within the semantic framework. Conceptually, the paper demonstrates that standard quantum theory can be realised as a structurally faithful subspace of a broader semantic state space, coexisting with gradient-flow and free-energy dynamics on probability measures. This establishes the mathematical foundation for coupling quantum dynamics to semantic field theories and complex-system models developed in subsequent parts of the programme.