A Language for Nearness: Why Medicine Needs Measures of Dynamic Fragility

This paper argues that medicine lacks a precise way to describe how close a biological system is to irreversible change. If disease is dynamic, transitions are non-linear, and systems lose recovery capacity before collapse, then a measure of nearness to transition is not optional but logically required. The paper develops this argument in three steps:(1) disease is better understood as a trajectory than as a static state;(2) biological change is inherently non-linear, making timing and sensitivity central;(3) loss of recovery precedes structural failure, creating a critical pre-collapse phase. From these premises it follows that dynamic medicine must move beyond descriptive language and include formal expressions that define instability, recovery, and proximity to transition in an exact and testable way. The work situates the URM framework within this logic and explains why a composite measure based on fluctuation, delayed recovery, and weakened stability is not a stylistic choice but a structural necessity. The paper is conceptual and theoretical. It introduces no new experimental or clinical data. It is intended to clarify the logical foundations of dynamic medicine and to define why measures of nearness to transition are required if medicine is to take change seriously.