Why Trust Scores Fail

This paper argues that universal, cross-domain trust scores — from credit ratings and ESG scores to AI-generated trust metrics — face structural limits that better data or better models do not remove. The claim is not that scoring is never useful, but that compressing trust into a single comparable number, used for high-stakes allocation across contexts, recurrently fails. Trust is treated here not as a scalar quantity but as a contextual, relational, and time-dependent state. The paper identifies five recurring failure modes (context collapse, Goodhart's Law, epistemic centralization, irreversibility, and metric substitution for truth), illustrated through documented institutional failures (Enron, Wirecard, Volkswagen Dieselgate, the 2008 subprime crisis, and ESG rating practice). An informal impossibility argument — analogous in form to Arrow's theorem, not a formal mathematical proof — suggests that no single universal trust score can jointly satisfy context-independence, temporal stability, observer-neutrality, and manipulation-resistance. The paper then discusses proof-based verification as a complementary paradigm: for a bounded class of objective, checkable claims, the need for trust is reduced through local verification rather than measurement. Examples include Bitcoin proof-of-work, zero-knowledge proofs, and blockchain-based supply chain traceability. The limits of this approach are discussed explicitly, including the oracle problem and the irreducibly judgmental claims that proof cannot settle.

This is version 2.0, a substantial revision repositioning the work from a position paper toward a conceptual analysis: the central thesis is qualified, an explicit scope-and-limitations section is added, the impossibility argument is reframed as informal, and the limits of proof-based verification are addressed directly.