A category behaving like Set: finite limits, exponentials, and a subobject classifier Ω. Elementary toposes host intuitionistic higher-order logic; Grothendieck toposes are categories of sheaves on a site.
A category behaving like Set: finite limits, exponentials, and a subobject classifier Ω. Elementary toposes host intuitionistic higher-order logic; Grothendieck toposes are categories of sheaves on a site.