The fourth mode of reason: “what I am willing to live as true.” The commitment register ℝeg_C stands alongside the empirical register ℝeg_E, the practical register ℝeg_P, and the diagrammatic register ℝeg_D as a structurally independent mode of engagement with reality. ℝeg_C-claims are not propositional assertions but performative declarations of lived commitment. Explicit admissibility rules prevent ℝeg_C from collapsing into dogma. The chapter addresses what was traditionally called “faith” without importing theological vocabulary, treating it instead as a structural universal property of the register architecture.