Each volume in this series represents an in-depth chapter in a history of philosophy. An author or current of thought is discussed in each. The «Introductions» provide essential critical information about philosophy and philosophers, and take into account recent historiographical research. This volume exhaustively reconstructs the principal historical stages of one of the most enigmatic cultural movements of the Ancient World, from its birth in VI century B.C. to its extinction in the IV, and its renaissance in the Imperial Age.