A Channel-Theoretic Taxonomy of Invariance

Any embedded receiver operating a capacity-limited channel—one whose capacity is insufficient to span its input space—necessarily partitions that input space into equivalence classes. The invariance properties of these classes generate a four-level taxonomy. Level 1 features are invariant under all physically realizable channels; Level 2 features are invariant across channels that share a constraint profile; Level 3 features are channel-specific. Level 4 is the formal boundary of the derivation: whatever, if anything, lies outside the structural content of the channel. The first three levels are derived from three premises about physical receivers; the fourth is registered, not filled. The taxonomy replaces the binary subjective/objective distinction with a graded structure indexed by invariance class and parameterized by constraint tightness. Companion papers apply the taxonomy to universals (Severs, 2026a), structural opacity (Severs, 2026b), inter-scale equivalence classes (Severs, 2026c), and the structure of subjectivity (Severs, 2026e).