Essay on the Principles of Logic

Wolff's book defends the Kantian idea of a 'general logic' whose principles underlie special systems of deductive logic. It thus undermines 'logical pluralism,' which tolerates the co-existence of divergent systems of modern logic without asking for consistent common principles. Part I of Wolff's book identifies the formal language in which the most general principles of logic must be expressed. This language turns out to be a version of syllogistic language already used by Aristotle. The universal validity of logical principles, as well as the translatability of other logical languages into this language, are shown to depend only on the meanings of its logical vocabulary. Part II of the book answers the metalogical question concerning the deductive relation between general logic and special logical systems, which also have their own (less general) principles. This part identifies the rules according to which logical rules can be derived from principles. The main result of the book is that the highest principles of logic and metalogics are provided by the syllogistic, when properly understood.