Opportunity-Conditioned Evidence From Absence: Why a Missing Trace Matters When Accounts Differ in What Should Be Found

This conceptual paper introduces Opportunity-Conditioned Evidence From Absence, the structural constraint that a missing trace discriminates between accounts only to the extent that they differ in the probability of finding no trace under the observation conditions. Its evidential force depends on opportunities for traces to arise, their detection and recording, and their retention and retrieval. The paper assesses absence by comparing what each account predicts would be findable. Absence can be strong evidence when finding no trace is much more likely under one account than another. Finding a record and validating it are distinct questions. The boundary with Negative Evidence Conditioned on Capture and Retrieval remains provisional. The discussion relates the constraint to Walton’s analysis of arguments from ignorance and examines the U.S. Fish and Wildlife Service’s 2021 extinction proposal and 2023 deferral concerning the ivory-billed woodpecker. The paper’s interpretation connects the case to search coverage, detectability, and disputed records. It does not settle whether the species persists. Part of the Possibility and Counterfactual Structure series within On Human Modeling, the paper offers questions for assessing what missing evidence can show. Its framework can inform human–AI research on whether missing search results, reports, or logs support conclusions about underlying events.