This book is a translation of Vom Wesen der Wahrheit: zu Platons Hohlengleichnis und Theatet. The text is based on a lecture course delivered by Heidegger at the University of Freiburg in the winter semester 1931-32. Part One of the course provides a detailed analysis of Plato's allegory of the cave in the REPUBLIC, while Part Two gives a similarly painstaking exegesis and interpretation of a central section of Plato's THEOAETETUS. The point of his interpretative method is to bring to light the original meaning of philosophical concepts, especially to free up these concepts, which in the subsequent tradition have become overlaid by secondary and even quite different meanings, to their intrinsic power.