Inside 206-105

Existential Pontification and Generalized Abstract Digressions

Logic

A classical logic fairy tale

(Selinger) Here is a fairy tale: The evil king calls the poor shepherd and gives him these orders. “You must bring me the philosophers stone, or you have to find a way to turn the philosopher’s stone to gold. If you don’t, your head will be taken off tomorrow!” What can the poor shepherd do […]

An Interactive Tutorial of the Sequent Calculus

You can view it here: An Interactive Tutorial of the Sequent Calculus. This is the "system in three languages" that I was referring to in this blog post. You can also use the system in a more open ended fashion from this page. Here's the blurb: This interactive tutorial will teach you how to use […]

Many-valued logics and bottom

I was flipping through An Introduction to Non-Classical Logic by Graham Priest and the section on many-valued logics caught my eye. Many-valued logics are logics with more than the usual two truth values true and false. The (strong) Kleene 3-valued logic, sets up the following truth table with 0, 1 and x (which is thought […]