The Universal Solvency Principle: A Standalone Selection Law for Persistence Under Constraint

We formalize a domain-independent selection principle governing the persistence of structures in finite environments. The principle asserts that a structure cannot persist or scale unless the value of its externally relevant uncertainty reduction exceeds the total cost required to maintain it, subjected to an explicit accounting protocol and a pre-registered decision task defining relevance. We resolve unit consistency by defining solvency in energy-equivalent (or currency-equivalent) units via a value functional tied to decision loss reduction, with a conservative physical lower bound derived from Landauer's limit. We provide full operational definitions for “externally relevant” information, a boundary closure and externality internalization rule for full cost accounting, and a rigorous control-theoretic corollary demonstrating effective contraction on a viable set. Finally, we establish a three-stage falsification protocol. Worked numerical examples are provided for a disturbed linear control system, a microbial energy budget proxy, and an economic decision service with diminishing informational edge.