What if life is not a loose checklist or a historical accident, but a structural threshold? Categorical Life is the sixth volume of the Panta Rhei series and the dedicated life layer of the architecture. It defines life through two earned predicates: Distinction, the formation of a stable self/non-self boundary, and SelfDesc, the internal decoding that allows a system to maintain and interpret that boundary from within. Three claims organize the volume: Life as enrichment: life is a genuine layer beyond physics, not merely a complicated physical phase Self-decoding distinctions: the hallmarks of life follow from Distinction plus SelfDesc rather than from an external checklist Biology by structure: persistence, agency, source, closure, and the mixed consumer sector organize the biological world The volume unfolds that architecture across origin-of-life questions, metabolism, genetics, plants, fungi, animals, neural systems, ecosystems, and the cosmic life argument. It then opens the bridge to Book VII by locating consciousness at the threshold where self-decoding becomes self-modeling. This is the book where the framework claims that coherence becomes living. 53 chapters across 9 parts. 2nd Edition, 2026. Thorsten Fuchs and Anna-Sophie Fuchs are the authors of the seven-book Panta Rhei series.