Three approaches to congruence
Résumé
This paper is concerned with three methodologies to construct a congruence in a language (L, O) among which Frege's specific solution stands. The first construction is derived from Leibniz's principle that indiscernible objects should be identified. The second construction is apparented to Frege's solution by its use of a referential model. The third approach is our own solution to the problem in the framework of rewriting systems.