Lewis Carroll's method of trees: its origins in Studies in logic

Abstract

In 1894, Charles L. Dodgson (Lewis Carroll) developed a mechanical method to test the validity of complicated multiliteral statements using a reductio ad absurdum argument. The basic ideas are similar to those in Beth's "Semantic Tableaux" and their seeds can be found in papers by Peirce's students, C. Ladd and A. Marquand, that appeared in Studies in Logic (1683), edited by Peirce. Dodgson named his approach, the Method of Trees. It was virtually unknown until 1977 when W. Bartley published the second part of Dodgson's Symbolic Logic, a book thought to have been lost. In this paper we examine the Method of Trees closely and establish the semantic connections between it, Ladd's "inconsistent triad" and Marquand's logic machines.