Coupling Geometry: Empirical Tests in the Civilisational Domain

This paper tests the Coupling Geometry framework against the civilisational record. The framework's axiomatic foundation is presented in a companion paper. The present paper reports the evidence for the framework's empirical entailments. A portfolio of forty-four historical systems scored under a rubric whose LLM-based rubric-reapplication agreement clears the pre-registered threshold (ICC = 0.83–0.85) produces a scalar-coupling finding (first principal component variance 92–94% across scoring regimes), a fitted threshold C* ≈ 4.78 and a refractive-field exponent γ ≈ 1.50 under the v3 scoring. These estimates remain provisional pending blinded independent historian scoring. A formal simulation (CONSTRAINT) whose mechanics are coded without reference to the framework's predicted quantities reproduces ten of eleven benchmarks across two pre-registered independent seeds; the cascade-duration decay constant is stable to within 0.2% across seeds (a level consistent with both a tightly-determined mechanistic law and with sampling convergence at this seed's n ≈ 340 cascade events; the manuscript's §5.2 distinguishes), and the eleventh benchmark failed on both seeds and is recorded as a genuine unresolved prediction. Two non-civilisational pilots recover the coupling-to-refractive-field relationship with γ estimates that bracket rather than reproduce the civilisational value, evidence consistent with the framework's weak universality claim (structural pattern recurs with substrate-specific exponents) and inconsistent with its strong form (substrate-invariant exponents); metric-specification issues remain unresolved in the sovereign pilot. Three focal cases (South Africa, Song-Ming China, French Revolution) and a Late Bronze Age worked example demonstrate engagement with specific historical questions, with the French Revolution serving as a second civilisational test of the Identity Constraint Theorem (the first being a separate Byzantine case study, "Identity as Refusal: A Coupling-Architectural Account of the Byzantine Case,"). The external multi-analyst study remains the decisive outstanding commitment. Manuscript under review at Cliodynamics.