This volume consists of two lecture series given by Heidegger in the 1940s and 1950s. The lectures given in Bremen constitute the first public lectures Heidegger delivered after World War II, when he was officially banned from teaching. Here, Heidegger openly resumes thinking that deeply engaged him with Hoelderlin's poetry and themes developed in his earlier works. In the Freiburg lectures Heidegger ponders thought itself and freely engages with the German idealists and Greek thinkers who had provoked him in the past. Andrew J. Mitchell's translation allows English-speaking readers to explore important connections with Heidegger's earlier works on language, logic, and reality.