The Ancient Greek Atomists assumed atoms to be the basis of the world. It is however extremely difficult to ascertain how they reached this conclusion and how they pictured these indivisible particles. (Did they see them as compact essences which were so hard that they could not be cut, or did they see them as units which were theoretically incapable of division?) This book undertakes a detailed study of the Ancients' tradition and creates a new basis for the question of the origins and significance of atomism.