The Ontology of Probability in Quantum Mechanics

Abstract This paper develops Distributed Presence (DP) as a realist interpretation of quantum probability within the standard formalism of quantum mechanics. The problem it addresses is the ontological status of Born-rule probabilities in a single-world, no-hidden-variable setting: if the quantum state is physically real, what do its probabilistic weights represent prior to measurement? DP proposes that, relative to a contextually specified decomposition of the state (which selects the relevant set of possible channels), Born weights can be read as presence fractions. These express the degree to which the system is really present, prior to measurement, in each alternative channel made available by that context. They should not be understood as measures of ignorance, mere predictive devices, or hidden determinations. Rather, they function as ontological indicators of distributed presence. On this view, measurement is not the revelation of a pre-existing definite outcome, nor the branching of worlds, but the single-channel actualization of one outcome from an objectively structured field of prior possibilities. The paper shows how this interpretation provides a unified reading of superposition, measurement, wave-particle duality, and entanglement while remaining fully compatible with Hilbert-space quantum mechanics and without introducing new dynamics. Its contribution is therefore interpretive rather than empirical: it offers an explicit ontological account of what quantum probabilities measure and clarifies how a realist understanding of quantum chance may be sustained without collapse models, hidden variables, or many-worlds branching.