Levels of Description and the Burden of Crossing Them

This paper develops a functional-logical grammar for transitions among three roles in physical explanation: applicability conditions, theoretical content, and empirical application. It treats transitions themselves as first-class objects of analysis and asks what additional warrant is required when support established in one role is carried into another. The framework distinguishes condition types, transition-specific profiles, and case-specific satisfaction; identifies nine ordered transition routes; and introduces the notions of bridge burden, bridge discharge, and residual bridge debt. A transition is adequately certified not by independence from theory or modelling assumptions, but by failure-sensitivity: there must be a route by which inadequacy of the warrant could be exposed. The framework is applied to four cases—Neptune, Vulcan, black-hole ringdown overtones, and thermometry—and then to decoherence and the quantum measurement problem. The analysis is diagnostic rather than verdict-generating: it localises what a stronger claim still owes, constrains the form an adequate repair must take, and also permits abstention where dependence is epistemically benign. Version 2.0 substantially revises and extends the earlier preprint Levels of Description and Conditions of Applicability of Physical Explanation: A Functional-Logical Analysis.