Universal Logic conceptualizes a new logic, where the main inference connective is understood as 'meaning containment'. Classical logic plays a restricted role, applying to 'classical sentences', while the new logic is studied in depth with chapters on semantics, proof theory, and properties. Based on this logic, simple consistency is proved for naive class theory, also in conjunction with 'classical theories' such as a Z-F-style set theory. This book shows how the main set-theoretic and semantic paradoxes can be solved in a systematic way, which is conceptualized independently of the paradoxes themselves.