The Hellenistic philosophers and schools of philosophy are emerging from the shadow of Plato and Aristotle and are increasingly studied for their intrinsic philosophical value. They are not only interesting in their own right, but also form the intellectual background of the late Roman Republic. This study gives a comprehensive and readable account of the principal doctrines of the Stoics, Epicureans and various sceptical traditions from the death of Alexander the Great in 323 B.C. to around 200 A.D. Discussions are arranged topically in order to address underlying issues and to make clear what the different schools have in common and how they differ. At the same time the coherence of each system as a whole is emphasized.