On Ultrafilter Logic and Special Functions

Logics for ‘generally’ were introduced for handling assertions with vague notions, such as ‘generally’, ‘most’, ‘several’, etc., by generalized quantifiers, ultrafilter logic being an interesting case. Here, we show that ultrafilter logic can be faithfully embedded into a first-order theory of certain functions, called coherent. We also use generic functions (akin to Skolem functions) to enable elimination of the generalized quantifier. These devices permit using methods for classical first-order logic to reason about consequence in ultrafilter logic.