L’implicazione in C.I. Lewis. La nascita dell’implicazione stretta dagli scritti giovanili alla Symbolic Logic

The necessity of ordering the philosohpical path that leads Clarence Irving Lewis to the formulation of the systems of strict implication gives birth to this work of thesis. After a short general introduction about the life and the philosophical view of Lewis, which is not strictly related to the logical writings, the attention has been at first focused on the historical-philosophic period between the nineteenth and twentieth centuries the framework in which his logical studies are put in, and afterwards on one of the first debates about material implication which shows Bertrand Russell and Hugh MacColl as leading actors. Subsequently an analysis of the early writings of Lewis has been performed. This period started with Implication and the Algebra of Logic, published in 1912, and ended in 1918 with Survey of Symbolic Logic; and the subsequent revisions written in 1920 in the article A Strict Implication - An Emandation. For the first time, the theory of the strict implication has been shown. Chapter three is dedicated to the Symbolic Logic. This text is known as fundamental in the history of Lewis’ thought. Particularly, the work has been interested in a specific way to those chapters dedicated to truth-value systems and to the notions of implication and deducibility, central ideas in the Harvard’s philosopher logic system. Furthermore a section has been dedicated to the analysis of the systems of strict implication: S1, S2, S3, S4, S5, that represent the highest peak of the Lewis’ logical study.