More and more I see the psycho-physical problem as the key to the overall spiritual situation of our age, and the gradual discovery of a new (“neutral”) psycho-physical unitary language, whose function is to symbolically describe an invisible, potential form of reality that is only indirectly inferable through its effects, also seems to me an indispensable prerequisite for the emergence of the new hieros gamos [sacred marriage] that you predicted. Letter from Wolfgang Pauli to C. G. Jung, May 17, 1952
