The book is a newly arranged and revised English version of "Aufbau der Physik" by Carl Friedrich von Weizsacker. Some original chapters and sections have been deleted, and a new chapter about further insights and results of ur-theoretic research of the late 1980's and 1990's has been included. Carl Friedrich von Weizsacker combines the perspectives of science, philosophy, religion and politics with a view towards the challenges as well as the responsibilities of our time.