The Indefinables of Logic

The view that the fundamental principles of logic consist solely of the law of identity was held by Leibniz, ¹ Drobisch, Uberweg, ² and Tweedledee. Tweedledee, it may be remembered, ³ remarked that certain identities “are” logic. Now, there is some doubt as to whether he, like Jevons, ⁴ understood “are” to mean what mathematicians mean by “=,” or, like Schröder ⁵ and most logicians, to have the same meaning as the relation of subsumption. The first alternative alone would justify our contention; and we may, I think, conclude from an opposition to authority that may have been indicated by Tweedledee’s frequent use of the word “contrariwise” that he did not follow the majority of logicians, but held, like Jevons, ⁶ the mistaken ⁷ view that the quantification of the predicate is relevant to symbolic logic.