This Commentary provides the doctrinal, historical, and conceptual foundations for the four-layer identity decomposition (s, e, b, a), the first ontology capable of expressing identity as execution rather than configuration. Whereas the ontology paper formalizes the construct, this Commentary explains why identity required a decomposition, why four layers are both necessary and sufficient, and how the decomposition resolves long-standing failures in identity continuity, drift detection, attestation, provenance, and governance. The text situates the decomposition within the lineage of substrate-rooted identity research and demonstrates the structural insufficiency of descriptive models such as (H, E, M). It clarifies the minimality and irreducibility of the four layers, articulates identity as a layered and drift-bounded construct, and shows how attestation, temporal projection, and governance become coherent only within this ontology. The Commentary serves as a doctrinal exegesis: a conceptual map that reorganizes prior formal objects into a unified field of execution-realized identity. It establishes the decomposition as the canonical primitive for systems in which behavior emerges from execution, not configuration, and lays the groundwork for a new discipline centered on substrate-rooted identity.