The first edition of this book, half a century ago, was hailed by the reviewers, as "the best history of Greek philosophy", or as "a work of indispensable consultation for the student", so that the Kirk-Raven was consolidated quickly as the reference work in the field, reading and commenting on the most important fragments and texts of the pre-Socratics. The book traces in an admirable way the intellectual revolution initiated by Thales in the sixth century BC. until its culmination in the metaphysics of Parmenides and the complex physical theories of Anaxagoras and atomists in the fifth century BC.