  The most outspoken structuralist with respect to logical constants, who explicitly understands himself as such, is Koslow. In his Structuralist Theory of Logic (1992) he develops a theory of logical constants, in which he characterizes them by certain “implication relations”, where an implication relation roughly corresponds to a finite consequence relation in Tarski’s sense (which again can be described by certain structural rules of a sequent-style system). Koslow develops a structural theory in the precise metamathematical sense, which does not specify the domain of objects in any way beyond the axioms given. If a language or any other domain of objects equipped with an implication relation is given, the structural approach can be used to single out logical compounds by checking their implicational properties.