Structural Decision: Decision as a Necessary Consequence of Admissible Persistence Architecture

This structure is not introduced here. It is already implicit in the Foundation Series and is isolated in the present paper. Papers D001–D003 derived structural time, information, and causality as necessary consequences of LP admissibility restriction. This paper derives structural decision as the fourth necessary consequence: the selection of one admissible trajectory from among the structurally available alternatives at any state in the LP phase space. The central claim: decision is not a psychological event, a rational computation, or a free act added from outside the structural framework. Decision is the structural selection of a causal path under admissibility constraint — already generated by Recovery Narrowing, already shaped by structural information, already ordered by structural causality. Three theorems are proven. Theorem D4.1 — Decision Space: at any state q, the set of admissible successor trajectories constitutes the structural decision space — the set of structurally available futures. Theorem D4.2 — Decision Narrowing: the structural decision space contracts monotonically as IR approaches 1. Theorem D4.3 — Irreversible Commitment: once an admissible transition is executed, the unchosen alternatives are structurally closed by causal dependency and temporal irreversibility. Corollary D4.4 (Class C) identifies rational choice theory, psychological decision-making, organizational strategy, and evolutionary selection as domain instantiations of structural decision. Decision is not the exercise of freedom over structure. Decision is what structure looks like from the inside — the moment at which one admissible causal path is executed and the others are closed.