What is philosophy? How does it differ from science, religion, literature, and other modes of human discourse? This course traces the origins of philosophy as a discipline in the Western tradition, looking to thinkers of Ancient Greece and Rome. We will examine how natural philosophers such as Thales, Anaximander, and Heraclitus distinguished their inquiries from the teachings of poets such as Homer and Hesiod; how ancient atomism had its origins in a response to Parmenides' challenge to the assumption that things change in the world; how Socrates reoriented the focus of philosophy away from the natural world and toward the fundamental ethical question, how shall I live? We will also examine how his pupil, Plato, and subsequently Aristotle, developed elaborate philosophical systems that address the nature of reality, knowledge, and human happiness. Finally, we will examine the ways in which later thinkers such as the Epicureans and Stoics transformed and extended the earlier tradition.