1. Notion and purpose of logic. The word logic has been used for several different kinds of mental activity throughout the history of Western thought. It covers matters as diverse as the syllogistic of Aristotle, the technique of Scholastic disputation, the transcendental logic of Kant’s Critique of Pure Reason, the dialectical logic of Hegel and the mathematical logic of our own days. The wide use of the word may be justified by understanding logic as the most characteristic element of a theory of rational discourse — that element which in i…