topos

OBS: Comparer à locus-loci.

CONT: The word topos was used for any category whose structure is sufficiently like Set, the category whose objects are crisp sets and whose morphisms are the set functions. It topos, basic set-theoretical constructions behave much as they do in Set itself. ... The principles of classical logic are represented in Set by operations on a certain set ... the two element Boolean Algebra. Each topos has an analogue or this algebra, and thus, each topos has its own logical calculus. This calculus differs from classical logic. In general, the logical principles that hold in a topos are those of intuitionistic logic, which does not accept the principle of excluded middle.