Diagoras of Melos (a lyric poet, 5th cent. B.C.) receives special attention for some time now because he was regarded in antiquity as a radical atheist. As the author of a prose work on atheism he was notorious for revealing and ridiculing the Eleusinian mysteries and was condemned for impiety at Athens. The present book evaluates the evidences for the biography of Diagoras and shows that he cannot be judged as an atheist in the modern sense.