This volume contains the lectures on Greek philosophy dictated by Giorgio Colli at the University of Pisa from 1965 to 1967, devoted to Gorgias and Parmenides, compiled by Ernesto Berti, one of his students. Complements the lessons compiled in Zeno of Elea (Sixth Floor, 2006), issued a year earlier, and adds to the valuable construct erected by one of the greatest philosophers of the twentieth century. With his usual historical-philological method, Colli brings us back to the V century BC Greece, place and time of birth of Western philosophy. Crumbling all available sources, as well as interpretations and translations that have been made over twenty-five centuries, from Plato and Aristotle to Hermann Diels, the Italian philosopher and novel posits its own conclusions. There, he says, a way of continuity of Parmenides Gorgias, through Zeno, where the origins of thought are emerging. First come the fundamental concepts and some laws of logical thought, although it is not in his work a formal elaboration of the same or of dialectical discursive thought. This comes about Zeno, whose "destructive method" to the extreme radical application of rationality in denial from the opponents. The same method will be applied by Gorgias until, in the most elegant way to demonstrate logically that "nothing is', ie, to an extreme nihilism characterized by open destruction, by the reductio ad impossibile, which eventually mingle with the political rhetoric sphere and the desire for power. Between one and another point, the truth moves from an ontological status which raises unknowable to human understanding, a retóricopolítico statute in which it is embodied by the logical-rational man budgets. Colli points out that traffic and warns us, like thinkers in analysis, about the negative consequences of the constant application of reason, and the neglect of the radical difference between truth accessible to man and the truth of being unknowable, between doxa and Aletheia, so dear to modern society.