Limits on Reversal and Extension of Relations: Why a Relation That Holds One Way, Between Some, or in One Setting Does Not Automatically Hold Further

This conceptual paper introduces Limits on Reversal and Extension of Relations, a constraint on drawing conclusions beyond an established relation’s direction, parties, or domain. A relation holding one way does not by itself establish its reverse, justify passing it along a chain, or support applying it in a different setting. The paper distinguishes reversal, chaining, and transfer across domains. Its standard asks whether an inference states and supports the additional premises its extension needs. Some relations are symmetric or transitive, and some findings hold across settings. The constraint therefore concerns treating extension as automatic. How often people extend relations without adequate support remains a separate empirical question. The account relates the constraint to research on confusion of conditional probabilities and examines the Institute of Medicine’s 1999 assessment of marijuana as a gateway drug. The case distinguishes retrospective patterns among serious drug users from the proportion of marijuana users who later progress to serious drug use, and separates these questions from causal explanations. It does not assess the current state of gateway research. Part of the Relational Conditions and Dynamics series within On Human Modeling, the paper offers questions for identifying a relation’s scope, examining the assumptions behind its extension, and recognizing who is affected by conclusions that reach beyond the original evidence.