Il significato di 'non': Negazione e doppia negazione in Leibniz

Most studies on Leibniz’s treatment of negation focus on logical and semantic issues concerning term negation (A est non B) or its relation to predicate negation (A non est B), whereas the role of external sentence negation (non (A est B)) is often understated or even denied. This paper advances a different picture. First, it provides evidence that external negation plays a prominent role in Leibniz’s logical calculi. Second, it investigates the reasons why Leibniz introduces his operator of negation by means of the law of double negation, as though this rule of inference expressed the meaning of ‘not’. Finally, it stresses the importance of distinguishing between grammatical and logical contexts, and considers that Leibniz’s clearest formulations of De Morgan’s laws pertain more to rational grammar than to symbolic logic.