A Beginner’s Guide to Mathematical Logic introduces a reader to the subject of Mathematical Logic. The author, Raymond M Smullyan, wrote several books. This is one of the many books he wrote for the layman to get them to understand Logic.
From the cover of this book, one can see a statue of Aristotle, a portrait of George Boole, and a photograph of Kurt Godel. The book is organized somewhat like the cover, where it opens with basic Aristotelian Logic. The syllogism is used and Smullyan attempts in many cases to demonstrate the truth or falsity of statements. When we get to Boole the kid gloves come off and we are introduced to Boolean Algebra and Propositional Logic. This introduced rigor to the field of Logic and was an attempt to axiomatize all statements in mathematics. The main proponents of such an idea were Alfred North Whitehead and Bertrand Russell. Well, not really; they invented a language and system that could be used to attempt such a thing, but many mathematicians wanted to be able to “complete” mathematics. Of course, fans of the field know what happened next; Godel came along and presented a proof showing that such an action was impossible.
Smullyan explains how that happened in an easy to understand manner. All Godel did was create a sentence out of a mathematical phrase that said something like “This Sentence Is False.” The important part is that he used the rigor of the Principia Mathematica to do so, turning this logical machine into a double-bladed sword.
The book also talks about First-Order Logic, which has the little upside-down capital ‘A’ or the universal quantifier and the backward capital ‘E’ or the existential quantifier. It goes into Tableaux as well, so that you can verify truth statements and truth tables.
So the book covers all of that information. It does so in a manner that is easy to understand if you are paying attention. It presents practice problems for each chapter with solutions at the end explaining the answer. For example, chapter 14 contains a statement called Proposition 1. It says “If S is an extension of R, then all recursive sets and relations are definable in S.” The first problem of the chapter asks you to prove this Proposition.
I enjoyed this book and it introduced me to some ideas in mathematics that I am not completely familiar with.