Committed Presentism: A Single-History Ontology of Quantum Mechanics

Abstract

Committed Presentism is a single-history ontology of quantum mechanics: only the present exists, reality advances through one global now within a causal domain, and one already-decohered branch becomes actual while the others never do. The construction is finite-dimensional, coherent, populated by explicit models, reproduces standard quantum predictions on the algebras analyzed, and leaves local relativistic dynamics unchanged in the modeled sectors. Within that scope the committed present leaves no marginal signature on the pointer algebra, on unconditioned spacelike-separated marginals under a local commitment instrument, or on bounded regions under a factorized global instrument. Silence there is exact for every record overlap those instruments cover; full local-state equivalence requires the exact commit regime, and optimal discrimination between the reduced states stays at chance. Ensemble-mean energy is preserved in the commit regime. Hilbert-space and projector factorization underwrite the global no-signaling result, and do not carry directly into interacting quantum field theory or gauge theory. Base structure, eternalism, Committed Presentism, and Stein point-relative becoming therefore agree on every state assignment restricted to those algebras. Reality is the currently committed configuration and the locus of truthmaking; the future is open, not yet committed. The past is a prior configuration, not a stored region: where the present-compatible history fiber is non-singleton, the antecedent is not recoverable from present and law. Past-tensed propositions are grounded by the total present with its laws and boundary structure, gap-bearing exactly when they vary across that fiber. The present is the condition under which any reading is actual.