Rice's Theorem under Self-Modification: Elevation Operators and a Normal Form
Abstract
We ask whether it can be certified algorithmically that a self-modifying computational system preserves a safety property at its next step (preservation) and along its whole evolution (persistence). One step of self-modification is a total computable transformation of program indices, and preservation is the elevated property . When is extensional, is behavioural and Rice's theorem applies. When reads the code, is no longer behavioural, yet under uniform disruption (an inert wrapper encoding ) the s-m-n reduction that proves Rice's theorem works inside a single behavioural fibre, and inherits the halting degree: one pullback of Rice, at two scales. One step never exceeds the degree of ; persistence can be -complete for properties, even for extensional . We then isolate the mechanism shared by rewriting, supervision and system comparison: the semantic elevation operator, which wraps a base system and reacts to one finite event anchored to , entering or leaving the property. For this class the elevated property is or , determined by trigger and polarity alone; it inherits or its complement; and the safe region is not recursively enumerable. The Rice-Shapiro theorem restricts the polarity: a finite trigger can only enter a property and only leave a one. Four axes (functional, deductive, conformance to a reference, monitoring) are verified instances, and towers of supervisors do not lower the barrier. We exhibit -hard intensional operators outside the class and state the open characterisation problem.