The preferred basis is causal: The measurement problem in an ontology of actualization

Abstract

The "preferred-basis problem" — why does measurement produce definite outcomes in this basis rather than another — is treated in opposite ways by the interpretations of quantum mechanics: posited ab initio (spontaneous collapse), drawn from a contingent environment (decoherence), left to the choice of a framework (decoherent histories), avoided (many-worlds, pilot wave). We show that in the Time–Actualization ontology — where measurement is an instance of the universal process of actualizing quantum potentialities into events — the preferred basis is anchored in the causal past of the event, together with a readiness condition: which events that past has made ready to actualize. TA does not introduce a new selection mechanism: it identifies the environment of einselection with the already-actualized causal past — an environment that is not posited outside the formalism (unlike an external classical apparatus), but is part of the same substrate. This anchoring is covariant (it depends only on the causal order), and the definiteness of outcomes — the uniqueness of the outcome — is posited by the objective collapse (where decoherence does not supply it), not explained. We situate this answer in the map of interpretations and lay out its scope plainly: the Born rule remains imported from quantum mechanics, and the theory is empirically equivalent to it; the contribution is ontological — on the axis of the preferred basis, one fewer postulate than a collapse model, and an origin of the basis anchored in the causal structure — not a new prediction. A symmetric downstream mechanism — the redundant proliferation of the outcome into the causal future (quantum Darwinism) — in addition accounts for the inter-observer objectivity of the actualized fact, without deriving it.