Persia is home to one of the few civilizations in the world that has had a continuous tradition of philosophical thought lasting more than two and a half millennia. From the time Zoroaster brought the Gathas, the sacred scripture of Zoroastrianism, until today, it has had a philosophical tradition comprising diverse schools and various languages including Avestan and Pahlavi as well as Arabic and Persian. The West has seen surveys of Persian art and anthologies of Persian literature, but this work is the first to present a millennial tradition of philosophy in Persia in the form of translated selections and introductory sections for each period and figure. Existing translations have been used where possible but most of the selections have been newly translated for this work which, with the help of the explanatory introductions, makes possible an intellectual journey into a philosophical continent much of which has been uncharted for Westerners until now.