Scepticism, a philosophical tradition that casts doubt on our ability to gain knowledge of the world and suggests suspending judgement in the face of uncertainty, has been influential since is beginnings in ancient Greece. Harald Thorsrud provides an engaging, rigorous introduction to the arguments, central themes and general concerns of ancient Scepticism, from its beginnings with Pyrrho of Elis (c.360-c.270 BCE) to the writings of Sextus Empiricus in the second century CE. Thorsrud explores the differences among Sceptics and examines in particular the separation of the Scepticism of Pyrrho from its later form - Academic Scepticism - which arose when its ideas were introduced into Plato's Academy in the third century BCE. He also unravels the prolonged controversy that developed between Academic Scepticism and Stoicism, the prevailing dogmatism of the day. Steering an even course through the many differences of scholarly opinion surrounding Scepticism, Thorsrud provides a balanced appraisal of its enduring significance by showing why it remains so philosophically interesting and how ancient interpretations differ from modern ones.