In 1955, Martin Heidegger delivered the keynote address "Gelassenheit" in Messkirch. This speech became a key text for understanding his later work. Since the address was directed at the citizens of Messkirch, Heidegger articulated his groundbreaking questions particularly clearly and understandably: - What is the position of humans in the world and towards the world? - What is the relationship between nature and technology in the atomic age? - Can we adopt an attitude of "simultaneous yes and no" towards technology? - How can reflective thinking be practiced, and how can it be transformed into a "decisive play" in contrast to the prevailing calculative thinking? - How can we gain serenity in the face of the challenges of both the past and present: the serenity towards things and openness to the mystery? This speech demonstrates the enduring relevance of Martin Heidegger's thought.