Inquiry rarely evolves inside one fixed evidential space. New instruments, altered challenge classes, revised standards of measurement, and changing explanatory demands reshape what counts as publicly observable in the first place. The problem of this paper is therefore temporal rather than merely static: when does revision of an observational architecture remain globally coherent through time, and when does it force branch-dependent reclassification of what is visible and hidden? The core result is a dynamic descent theorem. Rectangular revision is exactly the condition under which evolving observational projections remain compositional through time, so that revising first and quotienting later agrees with quotienting first and then transporting revision downstairs. Its main consequences are a revision--observation commutation theorem, a branch-dependence theorem, and a rectangularity–theoreticity theorem: failure of rectangularity is the temporal analogue of nongluing, and architecture drift changes observability itself. The broader philosophical payoff is a structural reinterpretation of theory change. Rational order through time depends not only on coherent updating within a fixed public space, but on whether the public space itself remains temporally integrable.
Lorand Bruhacs (Tue,) studied this question.