Predicate Logic

This lesson introduces predicate logic in comparison and continuation of the previous two historical attempts at theorizing logic—Aristotelian syllogism and propositional logic.

Review of the first theory

Aristotle’s colossal contributions to the foundations of logic can never be forgotten, just like his contributions to almost all major knowledge domains.

Summary of Aristotelian syllogism

Aristotle laid the foundations for the formal study of logic but scoped his study to categorical syllogisms, restricted to four standard formsA proposition has to talk in terms of all, none, or some. of propositions. A syllogism is a form of deductive reasoning that consists of two premises and a conclusion. It typically involves categorical statements about relationships between categories or classes of things.

The power of the theory

Even with such constraints, logicians could represent many real-world situations and judge the arguments as valid or invalid. Here’s an instance of a valid form of argument:

By speaking of two categories in every proposition, the sentence structure creates qualitative and quantitative relations between the subjects and predicates. These are important features for those who want to ...