[Carl Friedrich von Weizsäcker and the interpretations of quantum theory]

What are 'interpretations' of quantum theory? What are the differences between Carl Friedrich von Weizsäkcker's approach and contemporary views? The various interpretations of quantum mechanics give diverse answers to questions concerning the relation between measuring process and standard time development, the embedding of quantum objects in space ('wave-particle-dualism'), and the reference of state vectors. Does the wave function describe states in the real world or does it refer to our knowledge about nature? First, some relevant conceptions in Weizsäcker's book The Structure of Physics (Der Aufbau der Physik, 1985) are introduced. In a second step I point out why his approach is not any longer present in contemporary debates. One reason is that Weizsäcker is mainly affected by classical philosophy (Platon, Aristoteles, Kant). He could not esteem the philosophy of science that was developed in the spirit of logical empiricism. So he lost interest in disputes with Anglo-Saxon philosophy of quantum mechanics. Especially his interpretation of probability and his analysis of the collapse of the state function as change in knowledge differ from contemporary standard views. In recent years, however, epistemic interpretations of quantum mechanics are proposed that share some of Weizsäcker's intuitions.