This volume deals with fundamental problems of the natural sciences and the philosophy of nature. The issues addressed touch upon the many research areas of Hans Primas, and they reflect both the depth and the breadth of his interests, ranging from nuclear magnetic resonance spectroscopy, theoretical chemistry, theory reduction, the measurement problem, holism and realism in quantum theory, to the dialogue between W. Pauli and C. G. Jung. Each individual contribution is prefaced by a short editorial introduction, relating diverse topics to each other and embedding them in a wider frame.