The essays selected for this book comprise ideas presented in oral or written form between 1972 and 2000, some of them originally in German or French. They are preceded by a biographical and topical introduction.As the title suggests, attention is directed on the one hand toward the material world which is viewed in its extreme spatial extensions of the universe and of the elementary particles. In particular, the fascinating notion of the void and its fluctuating energy is the subject of various discussions, as is the subdivision of material bodies and its limits. The latter as well as the limit of gravitational stability are depicted in a diagram leading to the ultimate point of the Planck mass and length.The other topic of the title is the spiritual realm which, as in the Introduction, is based on reflections and quotations from religious texts. This rather personal aspect is also apparent in the frequent mention of the author's teacher Wolfgang Pauli, who on the psychological side is associated with C G Jung and Marie-Louise von Franz and on the physical side with Albert Einstein and the author's colleague Ernest Stueckelberg.