All Category Theory

This group gathers theorems of category theory, the general language of mathematical structures and the maps between them. It covers abstract fixed-point and diagonal arguments stated for categories, and the fundamental results about topoi, the categories that behave like universes of sets. A theorem belongs here when its cited article places it in category theory or topos theory. Results about the algebraic structures that categories are often used to describe, such as groups and rings, are grouped elsewhere under Algebra, and results about logic and sets are grouped under their own fields.