It may not be too much to say that all the work Western philosophers have done over the past two thousand years was begun by the Pre-Socratics. The Phoenix Pre-Socratic series has been instrumental in recovering Pre-Socratic texts. As with earlier works in this important series, this volume aims to make an important portion of Pre-Socratic writings accessible to all those interested in ancient philosophy and the first phase of European natural science. We now have, for the first time in English a translation of the bulk of texts concerning the atomists, with commentary. The work contains a new presentation of the evidence for the thought of Leucippus and Democritus, based on the original sources. It includes a Greek text of the fragments, in a new selection, with facing English translation. The testimonia (all newly translated) are presented in a new selection, designed to clarify the structure of the atomists thought and to present their texts in their argumentative context as far as possible. The notes and commentary aim to reflect the complexity and diversity of their thought, with particular emphasis on their metaphysical foundations, psychology, epistemology and ethics. Sections on biology, astronomy and theology are also included. Complete indexes, concordances and bibliography are included.