The study of knowledge is one of the most difficult tasks of philosophy. This volume is an attempt to confront the problem of knowledge from two different perspectives. First, the author analyzes the diverse modes of thought that reflect themselves in language (Logic), second, knowledge is considered in its roots with a critical examination of the stages of the cognitive process toward the truth (Gnoseology). The book is precise and sufficiently interdisciplinary without straying from the central theme. It was first published in Italian by the Pontifical Urbaniana University, Rome.