Coherence Horizons and Informational Accessibility: Temporal Commensurability as a Structural Precondition in Multi-Scale Systems

This article introduces a conceptual and formal framework for analysing how tempo- ral incompatibility between dynamical regimes constrains informational accessibility across scales. The central proposal is that systems do not merely differ in spatial scale, material substrate, or causal coupling, but also in the characteristic timescales required for the re- construction of their states. I define the reconstruction timescale Trek of a regime as the minimal temporal window required to recover a stable and operationally usable representa- tion of its state under a specified observational or modelling resolution. From this, I define the coherence horizon between two regimes as Hc = log10 Trek,1 Trek,2 . The associated accessibility function, A(Hc) = exp(−αHc), is introduced as a heuristic measure of the expected degradation of informational accessibil- ity as temporal incommensurability increases. The framework, termed inter-regime decoher- ence, is not intended as a complete theory of consciousness, emergence, or causation. Rather, it offers a substrate-neutral structural constraint on the conditions under which information can remain accessible, integrable, or causally usable across regimes. The article situates the proposal in relation to ontic structural realism, interventionist causation, coarse-graining, renormalization, mechanistic explanation, and major theories of consciousness such as In- tegrated Information Theory, Global Workspace Theory, the Free Energy Principle, and temporo-spatial accounts. Several illustrative cases are discussed, including anaesthesia, cortical dynamics, quantum measurement, and ecological regime shifts. The article con- cludes by outlining limitations, operational challenges, and possible falsification routes. The central claim is modest: temporal commensurability may function as a candidate structural precondition for stable informational accessibility in multi-scale systems. Keywords: philosophy of science; inter-regime decoherence; informational accessibility; coher- ence horizon; temporal commensurability; reconstruction timescale; multi-scale systems; struc- tural realism; consciousness; emergence. DOI 10.5281/zenodo.21628498