Time Without a Clock: Future-Admissibility as the Source of Temporal Direction

We argue that temporal direction does not require an external clock or a privileged first instant. Time is the parameter that maximizes joint predictability among coupled observables under a minimal admissibility set. Given reversible microdynamics, the admissibility set restricts the space of attainable histories and thereby induces asymmetric gradients in the present, selecting an arrow without invoking teleology. This operational criterion unifies thermodynamic and cosmological arrows as instances of the same constraint mechanism: when admissibility suppresses late-time macroscopic complexity, the two arrows coincide; when the constraint flattens, effective time symmetry is recovered. We extend the framework across domains by treating grammatical constraints as admissibility sets over sequences, yielding an operational notion of discourse directionality defined by the same predictability maximization. Three toy models, a coarse-grained gas, a coupled lattice, and an FRW sketch with bounded late-time curvature, illustrate the mechanism and delimit its empirical signatures. Date: February 2026DOIPrimary archive: https://doi.org/10.5281/zenodo.18552401Secondary archive: https://doi.org/10.6084/m9.figshare.31295488SSRN: Pending assignment (ETA: Q1 2026)