The Periodic Table of Conflations: Six Blocks, Twenty-Four Domains, Three Errors

Background: Policy failures, stalled projects, and frustrated reforms recur across domains, yet no unified framework maps their common structure. Purpose: To construct a periodic table that classifies systematic errors by mechanism rather than domain, enabling cross-disciplinary diagnosis and prevention. Method: Drawing on three established failure modes—Goodhart's Law (proxy failure), path dependence (selection failure), and the McNamara Fallacy (intervention failure)—we map twenty-four domains across six blocks, testing whether each domain exhibits all three error types. Results: Every domain examined contains all three conflations. The table structure is invariant: columns represent error mechanisms (fixed), rows represent domains (extensible), and blocks cluster domains by what determines value. A cascade rule predicts error chains; a prediction rule enables discovery of unnamed domains. Conclusions: Three error types, not four, are necessary and sufficient to classify systematic failures across natural, social, organisational, policy, engineering, and health domains. The framework provides a diagnostic grammar for disappointment. Plain Language Summary: Things go wrong in three ways: we measure the wrong thing, we get stuck on the wrong path, or we pull levers that don't connect. This paper builds a "periodic table" mapping these three errors across twenty-four fields.