This unique collection of essays, published together for the first time, not only elucidates the complexity of ancient Greek thought, but also reveals Karl Popper’s engagement with Presocratic philosophy and the enlightenment he experienced in his reading of Parmenides. As Karl Popper himself states himself in his introduction, he was inspired to write about Presocratic philosophy for two reasons – firstly to illustrate the thesis that all history is the history of problem situations and secondly, to show the greatness of the early Greek philosophers, who gave Europe its philosophy, its science and its humanism.