The lecture held at the University of Freiburg during the winter semester of 1929/30 is exciting in two respects. On the one hand, it contains a broadly conducted analysis of the boredom only touched upon in the Freiburg inaugural lecture "What is Metaphysics?", and on the other hand, it offers an equally detailed determination of the essence of the organism and life – a theme that Heidegger only names in "Being and Time," Par. 12. "This lecture is probably the most significant that Heidegger has given, and it is almost a second major work." Rüdiger Safranski.