Validity through Predicate Logic

Beyond translating logical arguments to predicate logic syntax, the major objective of logic is to validate those arguments. This lesson covers the last step of employing predicate logic.

Building predicate logic on propositional logic

We know by now how predicate logic evolved out of categorical syllogism and propositional logic by taking into its folds the best of the previous two theories of logic. This evolution is represented in the illustration below.

It’s important to highlight here that predicate logic imports the technique for validating arguments from propositional logic. This only means that the entire set of rules of inference and substitution gets inherited by predicate logic as well. However, because propositional logic doesn’t have quantifiers and variables, a couple of new rules of inference are created.

Reviewing inference rules

There are only a handful of inference rules, but the following figure lists the three most frequently used. The same rules will be employed in this lesson as well.

Modus ponens ...