The Ontology and Semantics of Quantum Theory for Quantum Gravity

Abstract: Based on a clear ontology of material individuals, we analyze in detail the factual semantics of quantum theory, and argue that the basic mathematical formalism of quantum theory is just okay with (a certain form of ) realism and that it is perfectly applicable to quantum gravity. This is basically a process about 'cleansing' the formalism from semantic assumptions and physical referents that it doesn't really need (we use the term 'semantics' in the sense of the factual semantics of a physical theory, and not in the sense of model theory of abstract mathematics or logic). We base our study on the usual non-Boolean lattice of projectors in a Hilbert space and probability measures on it, to which we give a careful physical interpretation using the mentioned tools in order to avoid the usual problems posed by this task. At the end, we study a possible connection with the theory of quantum duration and time proposed in [arXiv:2012.03994, arXiv:2107.06693], for which this paper serves as a philosophical basis, and argue for our view that quantum gravity may show that what we perceive as change in the classical world was just (an ontologically fundamental) quantum collapse all along.