Empty domain

In first-order logic, the empty domain is the empty set, having no members. In traditional and classical logic, domains are restrictedly non-empty in order that certain theorems be valid. Interpretations with an empty domain are shown to be a trivial case by a convention originating at least in 1927 with Bernays and Schönfinkel (though possibly earlier) but oft-attributed to Quine's 1951 Mathematical Logic.