Introduction to Formal Logic Created 970924. Last change 980626. Formal Logic F ormal logic can come in several shapes and flavours depending on its use. I f one wants to be able to evaluate and manipulate logical expressions a system like the basic Boolean algebra is suitable.
Boolean algebra is a 'practical' system.
In such systems one derive 'truths' or theorems out of the derivation rules and the axioms. A is a theorem or not is often not so interesting. What one examines in systems like the NAQ system is rather the system itself and its abilities. T he large interest in such systems comes from the fact that they are more powerful than Boolean algebra and the like, and you could actually derive all rules of Boolean algebra in a system like the NAQ system, and also because one can prove that all systems of 'Principia Mathematica'- type are in a sense all equal. They are all as powerful as one other, and all theorems you can derive in one system you can derive in all other systems.