Coupling Geometry Case Study XXV: Tokugawa Japan, 1603–1868

This case study applies Coupling Geometry to Tokugawa Japan, and it carries a double burden that makes it unlike any other study in the portfolio: it presents the corrected structural analysis of the bakuhan system, and it places on the external record a retraction. The case was investigated in April 2026 as a deliberate stress test of two foundational claims, with eight pre-registered range predictions locked before evidence gathering. The original scoring reported all eight confirmed, a composite of C = 6.20, and a headline theoretical refinement — that high subsystem interdependence moderates brittleness at high coupling. The programme’s full v3 rescoring audit subsequently found that the critical indicator had been scored with inverted rubric direction: I5 measures subsystem interdependence, so Tokugawa’s 250–270 substantially autonomous domains correspond to low I5 (3.0), not high (7.0). The corrected composite is C = 5.4; the corrected pre-registration record is four of eight confirmed, the failures concentrated exactly where the direction error sat; the stability puzzle the refinement was built to solve — ten stable generations at supposedly brittle coupling — did not exist, because 5.4 is not in the portfolio’s brittle band; and the refinement is retracted. The corrected analysis that remains is substantive: the bakuhan configuration as moderate coupling with exceptional modularity — a shogunal centre controlling inter-domain relations, coinage, and foreign policy over han that set their own tax rates across a documented 15–70 per cent range; sakoku as the portfolio’s only chosen closure of the A6 envelope, with the Dejima aperture demonstrating that external closure and internal intellectual pluralism are orthogonal — six competing schools, two hundred domain academies, over eleven thousand commoner schools behind sealed borders; Perry’s arrival in 1853 as an envelope bypass by a threat category outside the system’s calibration range; and the Meiji reconfiguration as the most thorough post-shock institutional transformation in the comparison set, drawing visibly on the domain-level capacity the system’s modularity had preserved. The retraction is narrated in full because the programme’s accepted-falsifications architecture is its most distinctive methodological commitment, and this case is that architecture operating. Adversarial examination — by historians of Japan above all — is invited. Case Study XXIV: The Aztec Triple Alliance, 1428–1521 – Case Study XXVI: Yugoslavia, 1945–1999