2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100846In this paper I develop categorical foundations needed for a rigorous approach to the definition of conformal field theory outlined by Graeme Segal. I discuss pseudo algebras over theories and 2-theories, their pseudo morphisms, bilimits, bicolimits, biadjoints, stacks, and related concepts.171 pages. Index added, some references added, format improved. This work has been published in the Memoirs of the American Mathematical SocietyCategory TheoryMathematical Physics18C10, 18C20 (Primary); 81T40, 18A30 (Secondary)text