Cultivating Trees: Lewis Carroll’s Method of Solving (and Creating) Multi-literal Branching Sorites Problems

Abstract

Lewis Carroll has been credited for developing a “Method of Trees” for solving multi-literal sorites problems, which anticipates several aspects of contemporary “tableau” or tree systems of logical proof. In particular, Carroll’s method pioneers the use of branching paths as a means of displaying or illustrating inclusive disjunction. However, rather than focusing on the respects in which Carroll’s tree diagrams resemble contemporary tree systems, I propose to focus instead on significant aspects in which they differ. In particular, I will show how the sorts of multi-literal sorites problems that Carroll’s method of trees is designed to solve are particularly ill-suited for resolution by more contemporary tree methods. I will also show how Carroll likely used something like this method, not only to solve but also to craft some of the trickier logical puzzles for which he is also famous.

Keywords

• lewis carroll
• logic trees
• logic diagrams
• sorites
• tableau
• logic puzzles