Heidegger, one of the twentieth century's most original and important philosophers presents an elucidation of the work of Heraclitus, a pre-Socratic philosopher. "Heraclitus" offers the first full English translation of a work first published posthumously in German in 1979. The book comprises two lecture courses delivered by Heidegger at the University of Freiburg during the summers of 1943 and 1944. Heidegger presents an elucidation of the work of Heraclitus, a pre-Socratic philosopher famous as the author of "On Nature", the first sustained work of Greek prose.