Revision with unchanged content. This book deals about Hans Morgenthau's Weltanschauung through the application of a hermeneutic approach. Thereby, his work will be associated with the work of Georg Simmel, Alfred Schütz and Karl Mannheim. It will be suggested that a reconstruction of his Weltanschauung is essential, because otherwise one will not be able to understand his work. This occurred, since his work was not set into the tradition of German social sciences. It will be pointed out that, he was a fierce opponent of combing natural and social sciences. He also had a wide understanding of politics. Depending on the intensity, everything can be become political. Finally, the nation-state is not given, but only one form of human sociation. It will be also suggested that constructivist theorems can already be found in his work, if not generally within German social sciences at that time. Therefore, this book can also be understood as a fundament, in order to call into question the novelty of constructivism. This book targets academics and students of international relations theory as well as history of thought and anyone interested in general.